Nucleus bump on close (renamed again)

What follows is a general commentary, which is not directed at the OP of this thread or anyone in specific.

I think the real problem is one of competence.

It used to be that if you wanted a top shelf rifle, you had it built by someone who truly understood the craft and it left his hands as good as it could be. If you had a problem, you knew for sure who is responsible for it and who is supposed to make it right.

Two things have changed that dynamic:
1. The internet and all its "information"
2. The commodization of the bolt action rifle facilitated by things like:
A. Savage style barrel nuts
B. Chassis-style stocks that require no inletting and almost never require bedding
C. Drop in triggers

Now anyone can buy a box of parts and build himself a premium bolt action rifle. Most of the time things all work together and the "builder" is happy. Occasionally something doesn't play well with others for various reasons that are common cause variation and the DIY'er either has no idea how to solve the problem or worse thinks he understands the issue but really doesn't. That's when you start seeing threads claiming defects where they may not exist and shit just goes down from there.

I started noticing this trend when nitriding your own barrel/action/bolt/whatever became the cool thing to do. My first clue, being a professional mfg engineer who really knows what nitriding is and what it's used for, was when everyone started calling nitriding a coating. The amount of stupidity related to nitriding is endless in many gun forums, ar15.com being at the forefront of that. You have too many people with superficial (and often grossly incorrect) "knowledge" pontificating about technical subjects with no controls. Anyone who pipes up to point out the mistakes is ignored or argued with. In the case of nitriding, internet gun forums including this one quickly became flooded with amateur metallurgists and heat treaters dispensing advice that ranged from the dumb to the dangerous.

Long ago I decided I would never buy any used rifle where the seller advertised that parts of it had been nitrided unless I know for a fact that whatever was nitrided came that way from its manufacturer. Now it seems I'm going to add DIY precision rifles to that list because at the end of the day there is no one who will stand behind such a rifle (and with good reason) when something needs fixing beyond my capability.
 
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LOLWUT?

Make a pdf out of an e-mail and you have a no shit written record of what was said, to whom, by whom, and when. Even admissible as evidence in court.
A phone conversation followed by an email summarizing the phone conversation is the best coarse of action when dealing with warranty issues. The simple conversation usually gets the problem resolved, I imagine ARC has thousands of emails to sort thru with redundant questions about the Nucleus, a random email is likely to get put on the back burner.
 
@Jon_ARC was tagged in this thread three days ago, and he has been on since then.

Yep, which isn't a exactly a 'direct' contact when you're looking to interact with the company for an issue with their product. I'm still firmly on the side of "if you have an issue with their product pick up the phone and call them." If you haven't done that yet, continuing to complain here isn't really all that productive. They might see it here and respond, but in the meantime you've had what, 3 weeks(?) to reach out and call them?
 
I think it is a trigger problem causing the "click" after observing my Huber vs my Diamond. And, after the information in the failure to fire thread.

I will trade for or scrape together the money and buy the action from you for the pre-order price if you don't want to deal with it.

I am 99% sure much of all the failure to fire of the Nucleus and this "defect" are all trigger related. If it truly is defective, then I will deal with ARC.

I will post videos showing what I have found when I can make them.
 
I will add that my diamond cycles the same as if no trigger was installed, except, that the sear holds the pin back.

Without a trigger installed in the action, the bolt wants to close because the pin is pushing on the cocking ramp which imparts a force that acts to close the bolt.
 
This makes sense, my only complaint is bolt lift on mine. Huber two stage trigger, I can't one finger lift the bolt, its close but a little to heavy. But closing I feel absolutely no hang up what so ever. And I only have 30 rounds through it. So I'm hoping bolt lift will get better or if not I could time the trigger. So Im guessing mine is cocking 100% on open.
 
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This makes sense, my only complaint is bolt lift on mine. Huber two stage trigger, I can't one finger lift the bolt, its close but a little to heavy. But closing I feel absolutely no hang up what so ever. And I only have 30 rounds through it. So I'm hoping bolt lift will get better or if not I could time the trigger. So Im guessing mine is cocking 100% on open.

Doubtful that timing your trigger will change bolt lift at all. The lift is primarily determined by the steepness of the cocking ramps and the spring #.
 
This makes sense, my only complaint is bolt lift on mine. Huber two stage trigger, I can't one finger lift the bolt, its close but a little to heavy. But closing I feel absolutely no hang up what so ever. And I only have 30 rounds through it. So I'm hoping bolt lift will get better or if not I could time the trigger. So Im guessing mine is cocking 100% on open.
Timing the trigger wouldn't be likely to change this as @hereinaz mentioned. What did lower it on my rifle was adding some proper grease to the cocking cams instead of just using Rem Oil.
 
I have been following/lurking this thread only because I was experiencing some cock on close with the Nucleus running a Bix n Andy TacSport, and I’ll start by fully disclosing upfront that my knowledge and understanding of the intricacies of bolt action rifles are limited. What follows may be blatantly obvious to many, but it was an epiphany for a wanna be rifle nerd like me. Thanks to all of you above for sharing your knowledge and feeding my curiosity.

If you are having that hitch/catch on bolt close, I figured out a simple way to check if the issue is due to trigger timing (i.e., as many above have mentioned - the cocking piece is engaging the sear too early which then results in the firing pin spring being compressed an additional amount by you during bolt close). In other words, the hand off between the cocking piece and the sear is not “timed” correctly.

In the cocked position, the cocking piece rests against the bolt body, but if you take the small washer and screw that came with the nucleus used for bolt disassembly/reassembly and screw it into the back of your firing pin assembly you can continue to tighten the screw until the cocking piece is pulled rearward (i.e., away from the bolt body). In this case the washer and screw are holding the cocking piece back instead of the bolt body. Obviously, how much you then tighten the screw will dictate the amount of rearward travel of the cocking piece.

The relevance of this (and the really interesting bit/epiphany for me) is that you can then use this method to diagnose if the issue you are having with the hitch is due to trigger timing. Long story short, back that cocking piece up some amount, insert the bolt back into the action, and test bolt close. Obviously you can’t pull the trigger to release the sear, but there will (or should) come a point when the trigger is "timed" and the bolt will close like butter. If this does occur like it did for me, it is consistent with what others above have stated – the hitch is not a nucleus problem or a defect - it's a trigger timing issue.

If you take measurements on the cocking piece distance from some reference point (either bolt body or cocking piece shroud before and after the hitch goes away, you have the distance needed for proper timing.

I am admittedly no expert - just an enthusiast who likes to know how his stuff functions. So take what follows with MANY grains of salt.

By design, the nucleus lacks the ability for the use of a trigger hanger which would have allowed a relatively easily “time”. As a result, the other options (in no particular order):
1. Live it with.
2. Find a different trigger that has a more forward sear.
3. File the sear the amount measured above when hitch goes away.
4. File the cocking piece the amount measured above when hitch goes away.
5. File both some amount equal to the total.
6. Ask ARC pretty pretty please to machine you a cocking piece the amount shorter when the hitch goes away.
7. Take it to a smith.

Using this method to diagnose timing would at least allow you to explore option 2 by asking questions about sear location relative to trigger pins before purchase.

Options 3, 4, and 5 will most definitely void your warranty and likely introduce cascading issues that may not be worth it:
1. Alter firing pin protrusion resulting in light strikes.... but you can adjust that on the nucleus
2. Alter firing pin fall force - the pin is falling a shorter distance and the spring is less compressed - this must translate into less force. So I suppose you could get a stronger spring.
3. Probably others that I know nothing about.

Personally, I’m left undecided about how to proceed. I may just live with it, but may get bold and try to file the sear (mostly because I have a Bix N Andy TacSport, and you can easily order a replacement top sear in the event I totally eff it up).


Hope these musings are helpful to someone.
 
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What kind of grease do you recommend on the lugs?
I personally used Gun Butter's trigger and locking lug grease, but it's just because my local shop (that I work at) carries only their grease and oil which makes it convenient for me to use. It's pretty slick when applied, and I use it on my O/U shotguns too since it's got an easy applicator and seems to take most of the grime with it when I wipe it off after an event or practice.

It is expensive though, and I'm sure most similar greases and compounds at a lower price point would give good results as well. Shooter's Choice Gun Grease seems to be very similar (it's even the same color, fwiw) and is less than half the price if you're ordering online from Amazon. On a bolt gun you won't be wiping it on and off quite as much as on an O/U shotgun, so you could probably use standard white lithium grease and be just as well off since easy removal is less of a concern.
 
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I have been following/lurking this thread only because I was experiencing some cock on close with the Nucleus running a Bix n Andy TacSport, and I’ll start by fully disclosing upfront that my knowledge and understanding of the intricacies of bolt action rifles are limited. What follows may be blatantly obvious to many, but it was an epiphany for a wanna be rifle nerd like me. Thanks to all of you above for sharing your knowledge and feeding my curiosity.

If you are having that hitch/catch on bolt close, I figured out a simple way to check if the issue is due to trigger timing (i.e., as many above have mentioned - the cocking piece is engaging the sear too early which then results in the firing pin spring being compressed an additional amount by you during bolt close). In other words, the hand off between the cocking piece and the sear is not “timed” correctly.

In the cocked position, the cocking piece rests against the bolt body, but if you take the small washer and screw that came with the nucleus used for bolt disassembly/reassembly and screw it into the back of your firing pin assembly you can continue to tighten the screw until the cocking piece is pulled rearward (i.e., away from the bolt body). In this case the washer and screw are holding the cocking piece back instead of the bolt body. Obviously, how much you then tighten the screw will dictate the amount of rearward travel of the cocking piece.

The relevance of this (and the really interesting bit/epiphany for me) is that you can then use this method to diagnose if the issue you are having with the hitch is due to trigger timing. Long story short, back that cocking piece up some amount, insert the bolt back into the action, and test bolt close. Obviously you can’t pull the trigger to release the sear, but there will (or should) come a point when the trigger is "timed" and the bolt will close like butter. If this does occur like it did for me, it is consistent with what others above have stated – the hitch is not a nucleus problem or a defect - it's a trigger timing issue.

If you take measurements on the cocking piece distance from some reference point (either bolt body or cocking piece shroud before and after the hitch goes away, you have the distance needed for proper timing.

I am admittedly no expert - just an enthusiast who likes to know how his stuff functions. So take what follows with MANY grains of salt.

By design, the nucleus lacks the ability for the use of a trigger hanger which would have allowed a relatively easily “time”. As a result, the other options (in no particular order):
1. Live it with.
2. Find a different trigger that has a more forward sear.
3. File the sear the amount measured above when hitch goes away.
4. File the cocking piece the amount measured above when hitch goes away.
5. File both some amount equal to the total.
6. Ask ARC pretty pretty please to machine you a cocking piece the amount shorter when the hitch goes away.
7. Take it to a smith.

Using this method to diagnose timing would at least allow you to explore option 2 by asking questions about sear location relative to trigger pins before purchase.

Options 3, 4, and 5 will most definitely void your warranty and likely introduce cascading issues that may not be worth it:
1. Alter firing pin protrusion resulting in light strikes.... but you can adjust that on the nucleus
2. Alter firing pin fall force - the pin is falling a shorter distance and the spring is less compressed - this must translate into less force. So I suppose you could get a stronger spring.
3. Probably others that I know nothing about.

Personally, I’m left undecided about how to proceed. I may just live with it, but may get bold and try to file the sear (mostly because I have a Bix N Andy TacSport, and you can easily order a replacement top sear in the event I totally eff it up).


Hope these musings are helpful to someone.

I hadn't got into thinking of how to measure it, but that is pretty good stuff. Thanks for sharing. I don't see any reason that wouldn't work. I am OK with option 1, truthfully. But, I wouldn't mind eliminating it. I'm gonna think on 3-7, and maybe even ---8--- get a second cocking piece from ARC and file on it, lol.
 
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I called and left another voicemail today, and this time got a call back. I will be sending my receiver, bolt heads, and trigger to ARC so they can check it out.

If you don't mind, will you please keep us updated. I'm waiting to see what happens to yours to decide what I'm going to do. For now, I'm living with it but if it can be fixed...
 
I called and left another voicemail today, and this time got a call back. I will be sending my receiver, bolt heads, and trigger to ARC so they can check it out.
Wow, almost a full month. And here I was pissed it took 16 days to get a condescending non-answer for my controlled round feed issues.
A company could have the best product in the world, but bad customer service really is a turn-off.
 
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Update 1

Got bold (stupid?) last night and decided to file on the cocking piece (I'll explain in more detail another reason why I decided to give it a go when I have more time to elaborate - suffice it to say that someone who know his shit said not to be afraid to file on a cocking piece but NOT a sear).

I used the method of measurement above as the guide for how much to take off. Took it off in stages, reassembled the bolt, and tested bolt close. Repeated as needed. I'll not leave you in suspense, after fiddling with it longer than planned (yeah... that never happens) filing on the cocking piece to time the trigger did completely remove any hitch on bolt close. It is now smooth and effortless, and I'm very pleased with the results.

See the post-timing here. The last 8 seconds shows it the clearest with zero catch from the point at which small detent is compressed, lugs are engaging the locking surface, and the bolt body itself can rotate into the closed position.

Haven't had a chance to test for any primer strike issues - hopefully tomorrow. Will keep you posted.

WARNINGS/CAUTIONS:
1. I took a chance and it paid off, but be prepared to totally f-up your cocking piece. No joke - expect that you will f it up, and then you won't be disappointed when you do.
2. Probably best to order an extra cocking piece from ARC before attempting any modifications.
3. Sear and cocking piece mating surface geometries are CRITICAL and especially fickle bitches - pay close attention to the geometry on your cocking piece before modification.
4. Standard warning about making sure you have enough sear engagement for safe operation.
5. Standard warning to proceed at own risk.
 
To enhance the consumer’s understanding of a bolt action, I would like to explain exactly how the Nucleus works and why it works as it does.

The Nucleus is a three-lug bolt action and as such, a constraint is imposed on the amount of available bolt rotation. I designed the Nucleus to have 72 degrees of bolt rotation. In so doing, I stuck a balance between the rotation allocated to various functions that the action must perform. I think the balance struck is quite good because many Nucleus customers who are very experienced with bolt action rifles have demonstrated extremely high levels of proficiency with Nucleus based rifles. They have also demonstrated the accuracy potential of Nucleus based rifles by regularly shooting groups that closely approach the limit of what is possible with their ammunition.

The bolt cycle begins by lifting the bolt handle. In so doing, the bolt shroud, the cocking piece, and the bolt body rotate freely until the shroud contacts the receiver and the cocking piece is forced into contact with both the cocking cams of the bolt body and a slot cut into the bottom of the bolt shroud through which the cocking piece protrudes. This initial and small amount of rotation eliminates the clearance between the bolt shroud, cocking piece, and bolt body so that the reward camming of the coking piece-striker assembly can begin. It is at this point that the shooter will feel significant resistance to lifting the bolt handle because she must now do the work that will be stored as potential energy by the striker spring. While doing this work, there are at many pairs of surfaces within the action contacting one another under load. Hence, reducing friction between parts, even by small amounts, using surface treatments such as nitriding, or properly done DLC, or just good old-fashioned grease can significantly increase efficiency and decrease the effort required to lift the bolt handle. However, the largest contributor to effects resulting in heavy bolt lift is the pitch of the cocking cams machined into the bolt.

The pitch is defined as the distance the striker assembly will move axially (along the length of the bolt) for some bolt rotation. Mathematically, that amounts to the linear motion of the striker divided by the angular motion bolt and may have units of your choosing such as millimeters/radian or inches/degree. It is important to note, that as the pitch increases, the force required to lift the bolt handle will increase non-linearly. For example, the change in the force required to lift the bolt handle if the pitch is increased from, let’s say 2.0 to 2.5 inches/revolution, will be greater than it otherwise would have been if the pitch is increased from 1.0 to 1.5 degrees. A change of 0.5 in/rev has a greater detrimental effect at high pitch values that it does at low pitch values. Therefore, cocking cam pitch is something we pay close attention to.

The effects of increasing the cocking cam pitch are not limited to the interface between the cocking piece and the cams. Increasing the pitch increases the contact forces between numerous pairs of mating surfaces that slide against one another when the bolt handle is lifted. This increase in contact forces correspondingly increases the friction forces that work to impede the rotation of the bolt within the receiver.

As the bolt handle is lifted, the nose of the cocking piece will climb the cocking cam of the bolt until it comes to bear against the flat aft surface of the bolt. While this happens, the root of the bolt handle encounters the extraction cam which is machined into the receiver. The extraction cam serves to drive the entire bolt assembly rearward in order to extract the case from the chamber. The amount of bolt rotation allocated to the extraction cam and the pitch of the extraction cam is determined by the type of extractor used and its functional characteristics, the types of cartridges used, the body taper of said cartridges, and the estimated likelihood that reloaders will exceed maximum recommended pressures. The design of the extraction cam will drive the design of the forward closing cams machined into the forward end of the receiver. During the first 15-18 degrees of closing bolt rotation, the bolt locking lugs will engage the closing cams to drive a slightly oversized cartridge into the chamber. If the cartridge can freely enter the chamber, then the closing cams offer the clearance necessary to rotate the bolt closed as it spirals forward at a rate determined by the pitch of extraction cam at the aft end of the receiver.

Did you get all that? Good.

Now, with all that in mind, consider the following. The Nucleus was designed as a field action, and as such, it was designed under the assumption that the shooter will operate the bolt quickly. Afterall, I designed this action for precision rifle match competitors participating in timed events. Therefore, while designing the camming characteristics of the Nucleus, I chose to take advantage of the forward momentum of both the bolt and the shooters hand. That is why you feel a bump immediately after beginning to rotate the bolt closed if you choose to rotate the bolt slowly. I chose a design having the bump simply because doing so makes it possible to reduce the pitch of the cocking cam which decreases the effort required to lift the bolt handle. That bump results from the noses of the cocking piece falling partially back into the cocking cams machined into the back of the bolt before the locking lugs gain purchase within the receiver. Once there, the entire bolt assembly is essentially trapped between the cocking cams and the forward closing cams. If the bolt is operated slowly, this bump characteristic is more distinct and perceptible than it otherwise is if the bolt is cycled as I designed it to be, that is rapidly, or at least with alacrity.

That said, there are other ways to reduce the cocking cam pitch but those also come at a price. For example, I could have designed the Nucleus with a fat bolt, that is one having a main body diameter equal to the outside diameter of its locking lugs. Such a bolt would offer more space for a cocking cam but at the expense of compromised feeding. Optimal feeding characteristics result from a bolt body diameter equal to the head diameter of the cartridge being fed. Fat bolt designs also make controlled-round feeding much less effective if not completely ineffective, again because of the large disparity between bolt body diameter and case head diameter.

Remember, within 72 degrees, we must find the room for lost motion due to clearance between parts, effective primary extraction which also drives the closing cam geometries, and enough contact between the bolt lugs and the receiver to render the action safe when firing. The cocking cam doesn’t have to remain within the bounds of rotation reserved for bolt purchase which would make bump-free closure possible. Thus, I deemed it more advantageous to reduce bolt lift by elongating the cocking cam because of available bolt and hand momentum. Moreover, the tactile characteristics of the bolt cycle is discussed at length with experienced shooters during development. Once the cycle is understood, shooters tend to be receptive of ideas that may be new to them.

While cycling the bolt rapidly, I, and many others, do not notice the bump. If anyone has a good reason for cycling the bolt slowly, please share it, but do so with an explanation of why disturbing the rifle while closing the bolt is worse than disturbing it while opening the bolt. And be mindful of the fact that the magnitude of the forces encountered, and therefore the disturbance experienced while opening and retracting the bolt is much larger than that experienced while closing the bolt, assuming of course that the cartridge fits properly within the chamber.

And again, if you cycle the bolt quickly, as I assumed you would, the forward momentum of your hand and of the bolt does the work of driving through the bump for you, especially when using the heavy rifles commonplace among competitive shooters. While driving the bolt forward, the root of the bolt handle will engage the extraction cam, and the hand and bolt momentum will drive the bolt along the extraction cam initiating the rotation to drive the bolt over the bump to its closed position. Done properly, the bump is essentially imperceptible.

Lastly, just because you can purchase a bolt-timing job for bump free closure or watch a YouTube video sales pitch of it, that does not make bump-free closure correct or even desirable. As Bohem pointed out, literally millions of bolt action rifles have been produced with both cock-on-open and cock-on-close characteristics (Mauser, Springfield, Remington, etc.) and the fastest cycling rifle, the Lee Enfield, is 100% cock-on-close taking full advantage momentum. The guys designing bolt action rifles during the late 19th and early 20th centuries were really smart and virtually all of their work is still relevant today.

Yet another factor that determines the tactile characteristics of the bolt cycle is the interaction between the cocking piece and the sear (or sear bar as commonly referred to) of the fire control (trigger) assembly. I designed the Nucleus to operate with the Remington factory Model 700 fire control assembly. Understandably, aftermarket M700 triggers will seldom drop into an action without a noticeable change to the tactile characteristics of the bolt cycle. I really can’t do anything about this because I don’t make aftermarket M700 triggers. I know that some of you have observed the cocking piece dropping slightly when closing the bolt. Perhaps in the future we can offer cocking pieces that engage the sear a bit further forward.

That said, as a manufacturer of M700 compatible actions, I would encourage my industry colleagues to come together and establish a proper standard for the M700 sear – coking piece interface. Interested parties know how to contact me.

Regarding lubrication and light strikes (failure to fire), it is generally a good idea to lubricate all sliding surfaces within the action EXCEPT for the shaft of the striker (firing pin) that passes through the bolt shroud. Applying a viscous (thick) grease to this area will likely result in light strikes. Significant energy is required to shear a viscous fluid within a small gap at high rates. This energy can only come from the main spring and therefore light strikes can result. After receiving your action, fully disassemble your bolt and clean it with a solvent. Ensure that the striker and the bolt shroud bore through which it passes is dry and oil free. Carefully lubricate all other sliding surfaces with your favorite gun oil or grease. Also note that oils can dissolve grease causing it to flow into the gap between the striker and the bolt shroud.

Lastly, regarding public discourse and etiquette on forums, I would like to state the following. By his own admission, TexasTightwad, the person who initiated this thread lacks experience with bolt action rifles but nevertheless took it upon himself to publicly label functions that he doesn’t fully understand as defects. I find this offensive because, as I hope this reply has demonstrated, I and others put a great deal of thought into American Rifle Company’s products. Had he pointed out something of which we were unaware, my tone would be different. He, and all of us, would be well advised to refrain from such public discourse until a comprehensive understand of the matter in question becomes available. Demonstrating ignorance is fine. One does so by simply asking a question. But it is not OK to be presumptuous and publicly demonstrate a lack of awareness that others may possess knowledge that you do not. Doing so can misinform those trying to learn or may lead knowledgeable people to call your intellect and trustworthiness into question.

TexasTightwad did contact us multiple times, but I can only respond to such inquires as time and interest allows me to. I did speak to him yesterday and encouraged him to send his action to us so that we may inspect it.

As you can imaging, composing this reply took considerable time. That said, I do realize that American Rifle Company leaves much to be desired regarding customer service. Maybe someday, we’ll be able to offer the level of service approaching that of MidwayUSA. But for now, I think that our limited resources are better spent designing great products and the processes for making them.

Ted
 
Ted,
It is unfortunate that you had to take the time to compose that response, but I appreciate how accurate and concise your answer was. While I do know how a bolt action bolt works, your explanation added some depth of knowledge that I did not previously have.

I did buy a Nucleus action and am enjoying it very much. I find that when it is actually used as a field action and not just played with at a kitchen table, it functions very well.
 
Ted,
It is unfortunate that you had to take the time to compose that response, but I appreciate how accurate and concise your answer was. While I do know how a bolt action bolt works, your explanation added some depth of knowledge that I did not previously have.

I did buy a Nucleus action and am enjoying it very much. I find that when it is actually used as a field action and not just played with at a kitchen table, it functions very well.

I concur 100%. My nucleus runs flawlessly in matches. It likes to be run hard.

I will buy another one soon.
 
To enhance the consumer’s understanding of a bolt action, I would like to explain exactly how the Nucleus works and why it works as it does.

The Nucleus is a three-lug bolt action and as such, a constraint is imposed on the amount of available bolt rotation. I designed the Nucleus to have 72 degrees of bolt rotation. In so doing, I stuck a balance between the rotation allocated to various functions that the action must perform. I think the balance struck is quite good because many Nucleus customers who are very experienced with bolt action rifles have demonstrated extremely high levels of proficiency with Nucleus based rifles. They have also demonstrated the accuracy potential of Nucleus based rifles by regularly shooting groups that closely approach the limit of what is possible with their ammunition.

The bolt cycle begins by lifting the bolt handle. In so doing, the bolt shroud, the cocking piece, and the bolt body rotate freely until the shroud contacts the receiver and the cocking piece is forced into contact with both the cocking cams of the bolt body and a slot cut into the bottom of the bolt shroud through which the cocking piece protrudes. This initial and small amount of rotation eliminates the clearance between the bolt shroud, cocking piece, and bolt body so that the reward camming of the coking piece-striker assembly can begin. It is at this point that the shooter will feel significant resistance to lifting the bolt handle because she must now do the work that will be stored as potential energy by the striker spring. While doing this work, there are at many pairs of surfaces within the action contacting one another under load. Hence, reducing friction between parts, even by small amounts, using surface treatments such as nitriding, or properly done DLC, or just good old-fashioned grease can significantly increase efficiency and decrease the effort required to lift the bolt handle. However, the largest contributor to effects resulting in heavy bolt lift is the pitch of the cocking cams machined into the bolt.

The pitch is defined as the distance the striker assembly will move axially (along the length of the bolt) for some bolt rotation. Mathematically, that amounts to the linear motion of the striker divided by the angular motion bolt and may have units of your choosing such as millimeters/radian or inches/degree. It is important to note, that as the pitch increases, the force required to lift the bolt handle will increase non-linearly. For example, the change in the force required to lift the bolt handle if the pitch is increased from, let’s say 2.0 to 2.5 inches/revolution, will be greater than it otherwise would have been if the pitch is increased from 1.0 to 1.5 degrees. A change of 0.5 in/rev has a greater detrimental effect at high pitch values that it does at low pitch values. Therefore, cocking cam pitch is something we pay close attention to.

The effects of increasing the cocking cam pitch are not limited to the interface between the cocking piece and the cams. Increasing the pitch increases the contact forces between numerous pairs of mating surfaces that slide against one another when the bolt handle is lifted. This increase in contact forces correspondingly increases the friction forces that work to impede the rotation of the bolt within the receiver.

As the bolt handle is lifted, the nose of the cocking piece will climb the cocking cam of the bolt until it comes to bear against the flat aft surface of the bolt. While this happens, the root of the bolt handle encounters the extraction cam which is machined into the receiver. The extraction cam serves to drive the entire bolt assembly rearward in order to extract the case from the chamber. The amount of bolt rotation allocated to the extraction cam and the pitch of the extraction cam is determined by the type of extractor used and its functional characteristics, the types of cartridges used, the body taper of said cartridges, and the estimated likelihood that reloaders will exceed maximum recommended pressures. The design of the extraction cam will drive the design of the forward closing cams machined into the forward end of the receiver. During the first 15-18 degrees of closing bolt rotation, the bolt locking lugs will engage the closing cams to drive a slightly oversized cartridge into the chamber. If the cartridge can freely enter the chamber, then the closing cams offer the clearance necessary to rotate the bolt closed as it spirals forward at a rate determined by the pitch of extraction cam at the aft end of the receiver.

Did you get all that? Good.

Now, with all that in mind, consider the following. The Nucleus was designed as a field action, and as such, it was designed under the assumption that the shooter will operate the bolt quickly. Afterall, I designed this action for precision rifle match competitors participating in timed events. Therefore, while designing the camming characteristics of the Nucleus, I chose to take advantage of the forward momentum of both the bolt and the shooters hand. That is why you feel a bump immediately after beginning to rotate the bolt closed if you choose to rotate the bolt slowly. I chose a design having the bump simply because doing so makes it possible to reduce the pitch of the cocking cam which decreases the effort required to lift the bolt handle. That bump results from the noses of the cocking piece falling partially back into the cocking cams machined into the back of the bolt before the locking lugs gain purchase within the receiver. Once there, the entire bolt assembly is essentially trapped between the cocking cams and the forward closing cams. If the bolt is operated slowly, this bump characteristic is more distinct and perceptible than it otherwise is if the bolt is cycled as I designed it to be, that is rapidly, or at least with alacrity.

That said, there are other ways to reduce the cocking cam pitch but those also come at a price. For example, I could have designed the Nucleus with a fat bolt, that is one having a main body diameter equal to the outside diameter of its locking lugs. Such a bolt would offer more space for a cocking cam but at the expense of compromised feeding. Optimal feeding characteristics result from a bolt body diameter equal to the head diameter of the cartridge being fed. Fat bolt designs also make controlled-round feeding much less effective if not completely ineffective, again because of the large disparity between bolt body diameter and case head diameter.

Remember, within 72 degrees, we must find the room for lost motion due to clearance between parts, effective primary extraction which also drives the closing cam geometries, and enough contact between the bolt lugs and the receiver to render the action safe when firing. The cocking cam doesn’t have to remain within the bounds of rotation reserved for bolt purchase which would make bump-free closure possible. Thus, I deemed it more advantageous to reduce bolt lift by elongating the cocking cam because of available bolt and hand momentum. Moreover, the tactile characteristics of the bolt cycle is discussed at length with experienced shooters during development. Once the cycle is understood, shooters tend to be receptive of ideas that may be new to them.

While cycling the bolt rapidly, I, and many others, do not notice the bump. If anyone has a good reason for cycling the bolt slowly, please share it, but do so with an explanation of why disturbing the rifle while closing the bolt is worse than disturbing it while opening the bolt. And be mindful of the fact that the magnitude of the forces encountered, and therefore the disturbance experienced while opening and retracting the bolt is much larger than that experienced while closing the bolt, assuming of course that the cartridge fits properly within the chamber.

And again, if you cycle the bolt quickly, as I assumed you would, the forward momentum of your hand and of the bolt does the work of driving through the bump for you, especially when using the heavy rifles commonplace among competitive shooters. While driving the bolt forward, the root of the bolt handle will engage the extraction cam, and the hand and bolt momentum will drive the bolt along the extraction cam initiating the rotation to drive the bolt over the bump to its closed position. Done properly, the bump is essentially imperceptible.

Lastly, just because you can purchase a bolt-timing job for bump free closure or watch a YouTube video sales pitch of it, that does not make bump-free closure correct or even desirable. As Bohem pointed out, literally millions of bolt action rifles have been produced with both cock-on-open and cock-on-close characteristics (Mauser, Springfield, Remington, etc.) and the fastest cycling rifle, the Lee Enfield, is 100% cock-on-close taking full advantage momentum. The guys designing bolt action rifles during the late 19th and early 20th centuries were really smart and virtually all of their work is still relevant today.

Yet another factor that determines the tactile characteristics of the bolt cycle is the interaction between the cocking piece and the sear (or sear bar as commonly referred to) of the fire control (trigger) assembly. I designed the Nucleus to operate with the Remington factory Model 700 fire control assembly. Understandably, aftermarket M700 triggers will seldom drop into an action without a noticeable change to the tactile characteristics of the bolt cycle. I really can’t do anything about this because I don’t make aftermarket M700 triggers. I know that some of you have observed the cocking piece dropping slightly when closing the bolt. Perhaps in the future we can offer cocking pieces that engage the sear a bit further forward.

That said, as a manufacturer of M700 compatible actions, I would encourage my industry colleagues to come together and establish a proper standard for the M700 sear – coking piece interface. Interested parties know how to contact me.

Regarding lubrication and light strikes (failure to fire), it is generally a good idea to lubricate all sliding surfaces within the action EXCEPT for the shaft of the striker (firing pin) that passes through the bolt shroud. Applying a viscous (thick) grease to this area will likely result in light strikes. Significant energy is required to shear a viscous fluid within a small gap at high rates. This energy can only come from the main spring and therefore light strikes can result. After receiving your action, fully disassemble your bolt and clean it with a solvent. Ensure that the striker and the bolt shroud bore through which it passes is dry and oil free. Carefully lubricate all other sliding surfaces with your favorite gun oil or grease. Also note that oils can dissolve grease causing it to flow into the gap between the striker and the bolt shroud.

Lastly, regarding public discourse and etiquette on forums, I would like to state the following. By his own admission, TexasTightwad, the person who initiated this thread lacks experience with bolt action rifles but nevertheless took it upon himself to publicly label functions that he doesn’t fully understand as defects. I find this offensive because, as I hope this reply has demonstrated, I and others put a great deal of thought into American Rifle Company’s products. Had he pointed out something of which we were unaware, my tone would be different. He, and all of us, would be well advised to refrain from such public discourse until a comprehensive understand of the matter in question becomes available. Demonstrating ignorance is fine. One does so by simply asking a question. But it is not OK to be presumptuous and publicly demonstrate a lack of awareness that others may possess knowledge that you do not. Doing so can misinform those trying to learn or may lead knowledgeable people to call your intellect and trustworthiness into question.

TexasTightwad did contact us multiple times, but I can only respond to such inquires as time and interest allows me to. I did speak to him yesterday and encouraged him to send his action to us so that we may inspect it.

As you can imaging, composing this reply took considerable time. That said, I do realize that American Rifle Company leaves much to be desired regarding customer service. Maybe someday, we’ll be able to offer the level of service approaching that of MidwayUSA. But for now, I think that our limited resources are better spent designing great products and the processes for making them.

Ted
Thank you Ted! I always look forward to your reply in these situations. I will be recieveing my action next week and and although I’ve read thru this thread I’m still as excited to receive it as the day I ordered it.
 
Ted - You're missing the forest for the trees.

The OPs issue was a significant hitch closing the bolt. He changed the title of his thread when he discovered burrs on the bolt lugs. A number of people offered possible causes which included trigger timing. The OP repeatedly indicated he eliminated that as a possible cause. He wasn't challenging the design of Nucleus, he was describing the symptoms of a function problem.

The offense you've felt is misplaced, and a 17 paragraph recitation of bolt design all but missed the mark. The OP said he was sure ARC would make things right and urged others not to call you just because of his thread. All you needed to say was, "Sorry you're having problems and it took us more time than I'd like to get back to you." To your credit, you owned up to this at the end.
 
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Ted - You're missing the forest for the trees.

The OPs issue was a significant hitch closing the bolt. He changed the title of his thread when he discovered burrs on the bolt lugs. A number of people offered possible causes which included trigger timing. The OP repeatedly indicated he eliminated that as a possible cause. He wasn't challenging the design of Nucleus, he was describing the symptoms of a function problem.

The offense you've felt is misplaced, and a 17 paragraph recitation of bolt design all but missed the mark. The OP said he was sure ARC would make things right and urged others not to call your just because of his thread. All you needed to say was, "Sorry you're having problems and it took us more time than I'd like to get back to you." To your credit, you owned up to this at the end.

It wouldn't be the first time that I failed to see the forest through the trees, but in this case I disagree with you, at least to some degree. The Nucleus may feel different from your favorite bolt action but for reasons that I think are very good, especially when considering the whole. And again, if anyone can present a good argument for bump-free closing after gaining understanding of how bolt actions work, I'm all ears. This would certainly not be the first time customers have driven a design change. Also bear in mind that all good arguments have factual underlying premises. So fire away...

In regards to the burrs emanating from the lugs of the bolt heads, I am withholding comments until I have the parts in hand. Photographs of machined parts are often misleading and I do not trust them.

Ted
 
It wouldn't be the first time that I failed to see the forest through the trees, but in this case I disagree with you, at least to some degree. The Nucleus may feel different from your favorite bolt action but for reasons that I think are very good, especially when considering the whole. And again, if anyone can present a good argument for bump-free closing after gaining understanding of how bolt actions work, I'm all ears. This would certainly not be the first time customers have driven a design change. Also bear in mind that all good arguments have factual underlying premises. So fire away...

In regards to the burrs emanating from the lugs of the bolt heads, I am withholding comments until I have the parts in hand. Photographs of machined parts are often misleading and I do not trust them.

Ted
I wasn't weighing in one way or the other on the Nucleus. I've shot one and it's a good action with several features which appeal to shooters who want the ability to use pre-fit barrels, at an attractive price point. I do think something is clearly wrong with the OPs Nucleus based on the video he posted. I'm sure you'll get it squared away.

With respect to your open question about the value of bump-free closing, it's my preference to have as little hitch/bump on closing as possible. I shoot PRS style matches where, while you may frequently run the bolt fast, there are nearly as many times where in a compromised shooting position, you have the target while on glass and it is beneficial to be able to chamber a round without losing sight of the target. Not necessarily slow, but deliberate. When supported by a bipod, the rifle will tolerate a higher hitch/bump on close. However, when shooting off a bag on the tip of a tank trap, a high level of hitch/bump on bolt close can roll the rifle off the bag.
 
To speak towards what Ted was talking about, with no hitch being noticed during practical use of the rifle, I can attest to that fact and recorded a short video to demonstrate this.

It's not the smoothest action out there, an Impact Precision or a Bighorn will feel more smooth when you close the bolt. I like the features and price point of the Nucleus, however, and the small design drawbacks (such as the "bump" described) are imperceptible when shooting a stage.

Video of the action in use

I had initial issues with light primer strikes. Since switching to a TriggerTech Diamond (which I had on order anyways) and dropping the bolt components into my ultrasonic cleaner to remove the protective oil/grease it ships with I have had no complaints about it. It's solidly built and most importantly (to me) feels exactly the same regardless of whether it's perfectly clean or absolutely filthy.

It gets really windy (30+ mph is common) where I shoot, and I often end up shooting down in the dirt and silt where my action ends up dirty. I previously used a Rem700 clone action with very tight tolerances that felt amazing right after cleaning it and rough as can be once a light breeze picked up (I had one match where I had to clean the bolt multiple times just to be able to cycle the action). The Nucleus has seen similar match conditions without me noticing a difference, which combined with the extractor and ejector makes for a robust design that I shouldn't have to worry about breaking.

It would appear though that the OP's action requires substantially more force to close past the bump than mine does. The bump on mine, while noticeable, is quite minimal.
 
@karagias
Ted, as Praeger said, I did not start this thread to bash your company; I started it because I thought that my trigger might be causing a problem. I want to see good companies keep making good products that shooters like me can enjoy.

Looking at the Nucleus, there was obviously a lot of thought put into it, and a lot of good design features for a price that is lower than many other actions. You are obviously a smart guy, and I certainly know less about bolt actions than you do.

Now that we are communicating, instead of fighting I'd much rather work together to resolve this issue. Can we do that?
 
I own 2 TL3's and picked up a second hand Nucleus today, all I can say is please people bash this action.... I need another Nucleus for my son and would love to get one cheap.

(Excellent action btw, I can really appreciate all the thought that went into it). Anyone got an extra Barloc with nut they wanna get rid of :)
 
What follows is a general commentary, which is not directed at the OP of this thread or anyone in specific.

I think the real problem is one of competence.

It used to be that if you wanted a top shelf rifle, you had it built by someone who truly understood the craft and it left his hands as good as it could be. If you had a problem, you knew for sure who is responsible for it and who is supposed to make it right.

Two things have changed that dynamic:
1. The internet and all its "information"
2. The commodization of the bolt action rifle facilitated by things like:
A. Savage style barrel nuts
B. Chassis-style stocks that require no inletting and almost never require bedding
C. Drop in triggers

Now anyone can buy a box of parts and build himself a premium bolt action rifle. Most of the time things all work together and the "builder" is happy. Occasionally something doesn't play well with others for various reasons that are common cause variation and the DIY'er either has no idea how to solve the problem or worse thinks he understands the issue but really doesn't. That's when you start seeing threads claiming defects where they may not exist and shit just goes down from there.

I started noticing this trend when nitriding your own barrel/action/bolt/whatever became the cool thing to do. My first clue, being a professional mfg engineer who really knows what nitriding is and what it's used for, was when everyone started calling nitriding a coating. The amount of stupidity related to nitriding is endless in many gun forums, ar15.com being at the forefront of that. You have too many people with superficial (and often grossly incorrect) "knowledge" pontificating about technical subjects with no controls. Anyone who pipes up to point out the mistakes is ignored or argued with. In the case of nitriding, internet gun forums including this one quickly became flooded with amateur metallurgists and heat treaters dispensing advice that ranged from the dumb to the dangerous.

Long ago I decided I would never buy any used rifle where the seller advertised that parts of it had been nitrided unless I know for a fact that whatever was nitrided came that way from its manufacturer. Now it seems I'm going to add DIY precision rifles to that list because at the end of the day there is no one who will stand behind such a rifle (and with good reason) when something needs fixing beyond my capability.
Exactly....

This guy among others have lots of Dunning-Kruger going on. In effect, they don’t know what they don’t know but because they are so confident that they do know... it becomes an issue.

Confidence is not capablity.
 
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I picked up two Nuclei earlier in the week and had the time to set one up and try it out this weekend. I also received two Barlocs that I haven't had a chance to put to use yet, but was impressed by. What a simple and ingenious way of locking down a pre-fit barrel.

I put a Trigger Tech special on the action, spun on a Bartlein barrel that I already had for one of my Mausingfields (which head spaced beautifully) and then dropped it into a Manners T4A mini-chassis. I put one of my often ignored NF NXS scopes (if someone could figure out a way to retrofit these to FFP, they could make a small fortune) on there just to get the chance to shoot the new action. I was pretty impressed with all aspects of the action. With the TT, the bolt cycled smoothly and without any hitches that have been described by some. I only fired 5o rounds, but I didn't have any light primer strikes and accuracy from a bench was sub 1/4", indicating uniform and sufficient ignition. I have most of the custom actions that people talk about on here, including another three lug action (M2013) and I really found nothing to find fault with when comparing the Nucleus to my other actions. When the price point is taken into consideration; it becomes even more impressive.

My other Nucleus is a left hand .380 for my son, and I only recently realized that none of my extras (with the exception of barrels) will work on this action, due to everything else I own being right handed. His birthday isn't until March though, so I have some time to piece it all together.

Overall, I'm impressed and definitely pleased with the Nucleus. I think Ted and company hit it out of the park. My only regret is not having ordered the extra 223 bolt head for my action when the pre-order was going on!

Added a couple of less than stellar pics because I recently realized how easy it is on the new site. Way to go Frank!
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Just for some more info... picked up my SA and LA Nucleus actions today. After fiddling with them it's apparent Ted put a lot of thought into the design, and everything is extremely well machined and finished. Bolt lug contact looks great, raceways look very nice, primary extraction cam contact looks great and is timed well, etc.

Going to build the SA first, so I put a CG Mod 22 trigger in it to play around with it on the bench. After installing the trigger the bolt feel does develop a "hitch" on closing when the bolt "hands off" the firing pin from the cocking cams on the back of the bolt body to the sear. Doing some measurements it appears the CG trigger is adding 0.026" additional cocking on closing which explains the "hitch" in the bolt travel; you either push firmly forward on the bolt handle to compress the firing pin spring that additional 0.026" or let the lead-in ramps on the bolt lugs add that extra 0.026" of firing pin spring compression. If you run the bolt fast and firm you don't notice it much, but if you try and work the bolt slowly it's very obvious. The shorter 72 degree rotation of the Nucleus bolt and the correspondingly steeper bolt lug ramps/helixes means it takes more bolt handle effort to "add" that extra 0.026" of firing pin spring compression compared to a 2 lug 90 degree action with more shallow and gradual bolt lug ramps/helixes.

Just off the cocking ramps on the bolt body the Nucleus gives about 0.250" firing pin travel; Ted states the Nucleus is 100% cock on open so that's the designed total firing pin travel. With the CG Mod 22 I'm getting 0.275" total firing pin travel. So even if I were to shorten the sear or cocking piece by 0.026" to eliminate the cock on close the action would still be getting the designed firing pin travel.

This is where a trigger hanger system with multiple offsets would come in handy, just swap to a -0.025" hanger and call it a day... but adding a trigger hanger would certainly add cost to Ted's "entry level" action and possibly also lead to minor stock/chassis mods for clearance. It would be very, very nice if Ted started offering multiple cocking pieces in say 0.005" increments from 0 offset to +/- 0.030" so you wouldn't have to modify any parts; just take a measurement and order the correct cocking piece... but that's a bunch of extra part numbers Ted would have to make and start stocking, plus a lot of potential phone calls and emails to deal with if people don't measure correctly and make the "hitch" worse (or go too far the other way and give up firing pin travel/energy and have light strikes.)

Going to call Tom at XTSP and see if he offers shorter sears, although I'd have to send the trigger back to have it swapped. If Tom doesn't offer different length sears, maybe I'll get a couple of spare cocking pieces from ARC (although given their production backlog I'd probably have to wait a couple of months.)

Also, the firing pin springs and the insides of the bolt body were 100% dry on my actions and not packed with grease as others who have experienced light strikes have reported.

Regardless, it's very apparent Ted put a lot of thought into the design, and I really like the action. Waiting on my barrel from Josh @ PVA, but I think I'll get the rifle together and shoot it before doing any sear or cocking piece mods to get rid of the additional cocking on closing. When shooting the rifle "normally" and not playing with it on the bench in the garage looking specifically for the slight "hitch" I might not even notice it.
 
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spun on a Bartlein barrel that I already had for one of my Mausingfields (which head spaced beautifully)

Glad I took the time to read through this thread as it addressed the one compliant I have about my nucleus and thoughts of what is going on. And then seeing this reply, it is money, I have a mausingfield too and I was curious if they would HS the same. Win/Win
 
Man, everyone in this thread seems to have way bigger problems than I do. Of course, I am still waiting (California) to pick up my Nucleus from the FFL, so there's that.

I saw my Nucleus in person a few days ago, and there's something that's been bothering me since then. There was a spot, a very small spot, near the back top of the receiver (blanking on the correct term), where it wasn't coated.

I'm not really interested in sending it back if I can avoid it, but I am concerned about the metal being exposed. It's a VERY SMALL spot, but for whatever reason that area didn't get the nitride treatment. I'm just worried about something going wrong with it later on down the road because of it.

I know, it sounds a bit like I'm making a mountain out of a molehill. Mistakes happen, and it looks like this could be a very small oversight, in the grand scheme of things. Butt least one or more people didn't see it before it was sent out, and that concerns me. I'm sure if I complained, ARC would fix it, but that's a hassle for everyone involved.

So if anyone has a solution that doesn't involve sending it back, like maybe something I can apply to it myself without ruining it, that would be cool.
 
To speak towards what Ted was talking about, with no hitch being noticed during practical use of the rifle, I can attest to that fact and recorded a short video to demonstrate this.

It's not the smoothest action out there, an Impact Precision or a Bighorn will feel more smooth when you close the bolt. I like the features and price point of the Nucleus, however, and the small design drawbacks (such as the "bump" described) are imperceptible when shooting a stage.

Video of the action in use

I had initial issues with light primer strikes. Since switching to a TriggerTech Diamond (which I had on order anyways) and dropping the bolt components into my ultrasonic cleaner to remove the protective oil/grease it ships with I have had no complaints about it. It's solidly built and most importantly (to me) feels exactly the same regardless of whether it's perfectly clean or absolutely filthy.

It gets really windy (30+ mph is common) where I shoot, and I often end up shooting down in the dirt and silt where my action ends up dirty. I previously used a Rem700 clone action with very tight tolerances that felt amazing right after cleaning it and rough as can be once a light breeze picked up (I had one match where I had to clean the bolt multiple times just to be able to cycle the action). The Nucleus has seen similar match conditions without me noticing a difference, which combined with the extractor and ejector makes for a robust design that I shouldn't have to worry about breaking.

It would appear though that the OP's action requires substantially more force to close past the bump than mine does. The bump on mine, while noticeable, is quite minimal.

Likely my last comment on this thread, I agree with Pretzel.

1) I shoot in the dust of the desert, and can't avoid all sorts of dust getting in my rifle. I am very happy with the Nucleus performance. I ran it in a dusty two day match and it ran flawlessley.

2) The "bump" on closing as designed into the Nucleus is nothing, and has so far had no significant effect to move me off target even from unstable positions, as I have a "hitch" which is more noticable than the "bump".

3) I am convinced that the "hitch" absolutely is a result of trigger/action interface. The machining and quality of the two Nucleus I have received is fantastic. When the trigger sear is too long, you get the hitch. If you read through some of the first of my comments on this post (well before the technical explanations), I first noticed that the hitch goes away if you push the cocking piece forward. Now I know that the sear is holding the cocking piece and bolt back far enough so that the lugs have to cam forward while compressing the spring more- and making the hitch.
 
I wanted to share my thoughts on a couple of things, and they are probably worth what they cost so take them with a grain of salt.

1. R700 triggers -- Ted mentioned it in his thesis a few posts above, but it doesn't seem to have caught any traction. There needs to be a standard for the relationship between the trigger housing mounting holes and the sear. If there was and all manufacturers followed this standard, then it would be a lot easier for action makers to design their actions to work with all R700 triggers. Seems like a no-brainer, but it hasn't happened yet. Until it does, we will have actions and triggers that work better with some combinations than others.

2. Alwayswatchyoursix, above mentioned a small imperfection in the finish on his action. I can understand how that would be mildly annoying, and without seeing it myself, I can't say what I would do about it. I would like to reassure him however that the nitrided dark finish is only surface cosmetics. The steel has been hardened and you really have nothing to worry about outside of aesthetics. As you use the action you will see that it (the dark finish) will wear in spots and that is normal. Anecdotally, I have one of the first Mausingfield actions that came out of the shop and it has nothing whatsoever done to it for a coating, literally straight out of the vibratory polisher and it is still defect free after 5 years. No corrosion, discoloration or anything at all. I'll try to add a pic of the uncoated action in a little bit.

3. I can't speak to every barrel that's ever been machined to mount on a Mausingfield, but I have tried three separate barrels that were made for my Mausingfields by two separate rifle smiths, and the headspace was perfect. Verified with Go and No Go gages as well as a piece of scotch tape on the go gage. Seems pretty amazing to me that it worked out so well.

Myself, I am looking forward to having a 22BR barrel spun up for my Nuke, and with help from my 10 year old son, putting together his 223 Nuke and going out and ensuring the local pronghorn and mule deer population has a little better chance of making it to the next hunting season.
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Update 1

Got bold (stupid?) last night and decided to file on the cocking piece (I'll explain in more detail another reason why I decided to give it a go when I have more time to elaborate - suffice it to say that someone who know his shit said not to be afraid to file on a cocking piece but NOT a sear).

I used the method of measurement above as the guide for how much to take off. Took it off in stages, reassembled the bolt, and tested bolt close. Repeated as needed. I'll not leave you in suspense, after fiddling with it longer than planned (yeah... that never happens) filing on the cocking piece to time the trigger did completely remove any hitch on bolt close. It is now smooth and effortless, and I'm very pleased with the results.

See the post-timing here. The last 8 seconds shows it the clearest with zero catch from the point at which small detent is compressed, lugs are engaging the locking surface, and the bolt body itself can rotate into the closed position.

Haven't had a chance to test for any primer strike issues - hopefully tomorrow. Will keep you posted.

WARNINGS/CAUTIONS:
1. I took a chance and it paid off, but be prepared to totally f-up your cocking piece. No joke - expect that you will f it up, and then you won't be disappointed when you do.
2. Probably best to order an extra cocking piece from ARC before attempting any modifications.
3. Sear and cocking piece mating surface geometries are CRITICAL and especially fickle bitches - pay close attention to the geometry on your cocking piece before modification.
4. Standard warning about making sure you have enough sear engagement for safe operation.
5. Standard warning to proceed at own risk.

Update 2

As promised, here is a range report post trigger timing.

Had a chance to get out yesterday. 100 rounds fired, and very happy to report zero issues. My Nucleus was functionally flawless, and the action ran smoothly and effortlessly.

To summarize, my Bix n Andy TacSport did sit in a spot in the Nucleus that resulted in some cock on close (placing the sear farther back than ideal). By my measurements in the 0.025" range - (probably resulting from stacked tolerances) - this is very similar to the measurement reported above by Kiba and consistent with what many others (see hereinaz immediately above) have said about what is causing the hitch.

Pre-timing, my hitch (again NOT the bump to start bolt body rotation) was quite noticeable even cycling fast. I can only speak from my own experiences with my Nucleus, but now that trigger is timed correctly I will unequivocally attest to the fact that the "bump" is imperceptible if run at any reasonable speed. It is truly a slick, robust, and well-designed action.
 
Good info, glad to hear it worked for you. I need to email ARC and backorder a couple of cocking pieces to play with.

I agree with Ted that the actions are functioning as designed (and well-designed at that.) Any excessive “hitching” on bolt close is most likely due to overcocking caused by variances in the location of the trigger sear vs the pin locations in the trigger housing. As Ted mentioned several posts ago, none of this would be occurring in the first place if there was a standard amongst the trigger manufacturers defining the dimensional relationship between the trigger pins and the sear location.

Without the trigger manufacturers building to a standard that defines the trigger pin to sear dimensional relationship the action manufacturers can't nail down a “correct” location for the trigger pins in the action that will provide correct timing without overcocking with *all* triggers. Without that standard you’re left with other solutions such as adjustable trigger hangers and cocking pieces with different sear catch locations to adjust the trigger timing for whatever trigger is currently installed.

I bolted my bare Nucleus action in the stock last night to lay prone and work the bolt… and once in the stock the amount of “hitching” on close with the current 0.026" cock on close with the CG trigger feels about the same as my AIAT and AIAX which both have a little “hitch” after the bolt rotational lock pin gets depressed and the bolt lugs engage the matching lug ramps in the receiver. The AT/AX actions have quite a bit of cock on closing that cause that little “hitch” and extra effort on close; it’s quite a bit more than the 0.026” cock on closing that I’m seeing with the Nucleus and CG Mod 22 combo. Not only was I left wishing I had my 223AI barrel for this weekend, I also think I should have preordered 2 short actions to have a spare for a future build...
 
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