Nucleus bump on close (renamed again)

[ThePretzel]

I checked my Nucleus and saw the shorter lead in on the lug that has the ejector slot cut, but as others mentioned that's per design.I could not find any burrs on the bolt head nor could I feel any click when running my bolt.

The action doesn't have the lightest bolt lift nor the most silky feel to it. Don't get me wrong - it's pretty darn slick and it beats every other rifle I have, it's just that it's a touch off from an Impact Precision or a Bighorn in terms of how smooth it is and the bolt lift is a fair bit heavier than something like a Curtis Axiom.

That being said, that's not why I bought this action. I bought this action because I like the shorter bolt lift (more clearance so I don't either bang my knuckle on the scope or risk the knob hitting my finger's knuckle when it's on the trigger under recoil like a Christensen does for me) and because it's a very robust action. By robust I mean that I've heard good things about how the Mausingfield actions just work regardless of the conditions. My experience with the Nucleus (since I fixed the issue with Timney triggers causing light primer strikes) has been exactly that, the rifle feels damn near identical regardless of whether it's had dust and dirt blown into it all afternoon or if I just cleaned and lubed it. I've never had a hard bolt lift, close, or travel because it's gotten gummed up. I don't have to worry about the ejector ever really breaking.

It's also pretty darn beefy, weighing in at 4 lbs (64 ounces) compared to the 28 ounces of a Bighorn, the 32 ounces of a Lone Peak, or even the 56 ounces of an Impact Precision. The weight is a plus to me, since I want a heavy rifle anyways.

 

[hereinaz]

Yeah, you probably have nothing to worry about with the John Hancocks. As others have said, when they leave PVA they will have triggers installed, at which point if they had the same defect as mine it should get caught. I understand why it did not get caught at ARC. It's a very small detail in the midst of a lot of other details, and with no trigger on it there are no symptoms. We're all human and I am not upset that it happened, I just want it fixed.

I did not intend to scare people who are waiting on their orders. Just wait until it comes in and see. I am assuming ARC will take care of this, so as long as they do it's not a big deal to me.

I did however intend to find out if anyone else was having this problem, and make people aware that if their action is not acting right, it might be a defect that (I assume) ARC would be happy to fix. Better to have a fixed problem than have people trash-talking their actions.

@hereinaz Perhaps your bolt heads are cut correctly or at least closer than mine. It is a major catch on mine, and not tolerable on any rifle no matter the price point.



When I get home, I'll try to get some measurements from the bottom of the lead-ins to the grooves in each of the lugs.

A major catch is a different thing. And, your's could be more than mine for sure, tolerances being so tight. Bummer you have two having the problem. I was just trying to put perspective to it for anyone who ordered. Based on the Bix & Andy videos, I am wondering if it isn't a trigger dependent issue. And, we've got the post above saying two triggers operate differently.

I do think ARC will take care of genuine issues. And, again, burrs are another thing... Hope you do get it resolved.

 

[hereinaz]

I went back and played with my action. I think it is a cock on close issue, that click goes away if I push the bolt forward.

And, when looking at the back end of the bolt inside the shroud, I can see that when closing it, the firing pin looks to be moving back after cocking, indicating that the trigger is too far forward. I am going to talk with a smith about it, but I think it is a cock on close issue in my action at least.

If you close your bolt, without pulling the trigger, while you lift the bolt up, watch the back end of the firing pin in the shroud. You can see it moving out of sync. I think I can see where the bolt body moves back with the lugs disengaging, and the as the bolt rotates just a hair more, the firing pin disengages. I don't think it is timed as well as it could be.

If I watch the firing pin and shroud/body on the back side when I close it, I can the firing pin catch the sear. Then, as the lugs engage, as soon as it "clicks" the bolt body moves forward, while the pin stays where it is. This tells me that the sear is catching ahead of the lugs, and I am getting additional compression on the firing pin spring on the "click".

The front of my action/bolt looks exactly like the video posted when the lugs click.

Running the bolt fast, just the extra inertia is enough to make it completely disappear. But, if I move it slowly, I can see it engaging the different parts.

Someone might correct me, but I think that is what I am seeing.

I will do a video in a week or so, I am headed out of town.

 

[10ring1]

Please God, never utter that vile word on this site.

Haha. All in good fun...

 

[Edds]

......It's also pretty darn beefy, weighing in at 4 lbs (64 ounces) ..........

What did they do to it to make it that heavy?

 

[bohem]

I am replying from my phone standing in front of a lathe right now so please excuse the brevity up front. We just got 2 phone calls about this thread and I felt I need to respond before it gets totally upside down on our rifle due to internet broken-telephone


The JHR is something that will be double checked by 2 different people (Jeremy amd myself) per our internal, documented process in productiom assembly.

I have spoken to Ted a LOT on trigger interactions with the Nucleus in past months. I spoke with Timney about it for JHRs as well. We also ordered each JHR action with heavier main springs to avoid any potential light strike issues.

If there is something that needs to be addressed with reliability or interaction we have process control plans to handle that.

Until I can see a problem in hand I cannot go thru and describe a fix, but I can assure folks that we will address it before a JHR leaves.

 

[bohem]

I went back and played with my action. I think it is a cock on close issue, that click goes away if I push the bolt forward.

And, when looking at the back end of the bolt inside the shroud, I can see that when closing it, the firing pin looks to be moving back after cocking, indicating that the trigger is too far forward. I am going to talk with a smith about it, but I think it is a cock on close issue in my action at least.

If you close your bolt, without pulling the trigger, while you lift the bolt up, watch the back end of the firing pin in the shroud. You can see it moving out of sync. I think I can see where the bolt body moves back with the lugs disengaging, and the as the bolt rotates just a hair more, the firing pin disengages. I don't think it is timed as well as it could be.

If I watch the firing pin and shroud/body on the back side when I close it, I can the firing pin catch the sear. Then, as the lugs engage, as soon as it "clicks" the bolt body moves forward, while the pin stays where it is. This tells me that the sear is catching ahead of the lugs, and I am getting additional compression on the firing pin spring on the "click".

The front of my action/bolt looks exactly like the video posted when the lugs click.

Running the bolt fast, just the extra inertia is enough to make it completely disappear. But, if I move it slowly, I can see it engaging the different parts.

Someone might correct me, but I think that is what I am seeing.

I will do a video in a week or so, I am headed out of town.

I'm trying to figure out how to educate folks on this topic without coming across harsh or rude. THere is a propensity on here to talk about timing and trigger cock on close like it's a flaw in design. It seems to be a fundamental misunderstanding of how a bolt action receiver works and it keeps being dragged around forums as a complaint point. I think we need to at least talk about it to help folks understand because after reading a lot of this thread the misunderstanding about cocking force, cock on open, trigger timing, etc continues and the issues arise for all of us building rifles and working on receivers to keep customers educated and informed.


I'm not trying to single you out @hereinaz on purpose, your post is a perfect time to discuss what's going on in general with a bolt action receiver and the function of the mechanisms inside. Hopefully you won't take this as a slight as I'm not trying to, I'm just trying to explain how the stuff is functioning.

Cock on close is a design balance not an "issue", it's how actions work. Every action has a timing choice and it comes down to how a particular trigger fits in a receiver.
700's cock on close for 1/3 of the travel of the cocking piece. That's right, 35% of the cocking piece travel is done while closing the bolt.
Bighorn TL2's are ~15% cock on close
Bighorn TL3's are ~14% by design
Defiance Deviants are as well.


Mausingfields are 105% cock on open, -5% cock on close. AKA it overcocks on open by design.
That makes bolt lift heavier than it needs to be. It also means that the bolt closure feels like it snaps shut by itself because that's exactly what's happening.

The early GAP Tempest actions had massive overcocking on them, bolt lift was heavy but the bolt closure was actually assisted by the main spring itself and the effect was that it felt good to folks used to a 3 lug albeit with a heavy bolt lift... It also made the action feel faster even though it was less smooth.

Since the Nucleus is a 3 lug the split to put some cock on close exists to lighten bolt lift, again something that is a hot topic of debate around this forum.

The Seekins HAVAK action is 50/50. The bolt force is low on average but it feels odd because the bolt is constantly under a rotational restraint while opening and closing.

The trigger sear bar defines how much it is cock on close vs. cock on open.
There is a trigger made by timney designated as the "U" or extended sear.
It was developed in 2010 in conjunction with a now-defunct custom shop in Montana that brought the issue to Timney and went onsite to work with them. Lots of folks knew about it but those guys actually showed up and worked with Timney to get it into regular parts production.

The trigger manufacturers have different interactions with different actions. The individual triggers have as much to do with it as a design of an action does.

The governing equation to think about is the work being done.
If a bolt has a specific diameter and cocking stroke (let's use 0.7" nominal and standard 0.2" lift strokefor an apples to apples comparison) then the longer the angle a handle is rotated through for cocking the firing pin then the lighter the bolt force will be on average

Work = Force * Distance

Since the work involved is staying the same then the variables we're talking about are F and D. (There is probably a joke there, someone else can make it for me)

So, W is fixed.
We want F to decrease so therefore D must be as large as possible ((joke? that's what she said? nobody?))
Or if we want the shortest throw possible then the F will be large/hard (this seems like softballing in the setup here)

Nobody wants an action that has a 10 degree bolt throw but a 50lb bolt lift.
Conversely everyone wants a bolt we can open with 1 finger but we don't want to have a 180 degree throw to open it.
Everything is a balance.
In a 50/50 action we get that 180 degree throw. You have 90 deg to unlock and cock the bolt halfway, then another 90 to lock it and cock the other halfway. This is the lowest average force you'll get on bolt throw. Most folks don't like it though because we've been conditioned as shooters to have a light bolt closing stroke.

Now, there are safety aspects to it as well, but we can discuss those at a later time. Right now we're just talking about bolt lift vs. cocking piece timing.

You know how we say "Remington 700 CLone" and then the action doesn't quite fit the stock like it should? Same thing with triggers.
I just read somewhere on here that a guy stated "ARC Made the Nucleus footprint too close to a 700 to work with the lug lock on an MPA"

I just had to chuckle at that comment because it shows what people will accept in the industry as "close enough" and when someone actually makes a part that truly matches the thing it's supposed to clone a bunch of other stuff falls apart. Then another component that's "close enough" doesn't fit the company that made the original product to what the advertising states is a the bad guy.

 

[TexasTightwad]

I tried to do some damage control once I saw there were some people freaking out! Please don't call ARC or PVA because of my thread unless you have thoroughly verified that there is a need to.

I am also standing in front of a lathe as I type this! As part of my "thoroughly verifying", I brought my action to work today where I have all of my precision measuring tools and fixtures.

I put the action in a fixture that immobilized it, put a .063" gauge pin in the firing-pin hole of the bolt, and put an indicator on the pin. I used the pin because there were no other surfaces I could indicate on that would give me the data I was after, which is radial movement. The indicator was oriented on the side in line with the lug in question. I set the zero while the bolt was locked, and it had about the same zero unlocked, but with minor variances because there is necessary clearance at that point. But while the lugs are contacting on the lead-ins (where my catch is) the bolt deflects .010" away from that lug. If everything was concentric, the bolt would rotate on the same center while on the lead-ins as it does while on the locking surfaces of the lugs.

I want to make sure I do every bit of due dilligence that I can before I contact ARC. Please do the same and don't contact ARC or PVA unless there is a need to.

P.S. @hereinaz I can eliminate the catch by pushing forward hard on the bolt too. The reason is that it allows you to skip right over the lead-ins. The purpose of the lead-ins is to bring the bolt all the way forward so it can lock up on the back of the lugs. If you push to where it is already there, it's not contacting on the lead-ins at all, just going straight to the locking surfaces. Your bolt could have no lead-ins at all and it would still work just as long as you always had the bolt pushed all the way forward as you rotated it.

 

[whatsupdoc]

So if I am understanding this, on closing the two bolt lugs with complete lead-ins are touching the receiver lugs while the third bolt lug with slot is not, causing the bolt to deflect.
The catch on bolt closing, is it doing it with and without a trigger installed or just with the trigger installed.

 

[TexasTightwad]

So if I am understanding this, on closing the two bolt lugs with complete lead-ins are touching the receiver lugs while the third bolt lug with slot is not, causing the bolt to deflect.
The catch on bolt closing, is it doing it with and without a trigger installed or just with the trigger installed.

You have it backwards. The lead-in next to the ejector slot (the one that had burrs which have since mostly worn off) is contacting first, causing the bolt to deflect. The other two may or may not be contacting, but if they are, it is not as soon as that one because they would keep the bolt centered.

The catch is only noticable with a trigger installed, and that's because the trigger loads the firing-pin spring causing the bolt to have to pull itself forward and overcome that rearward pressure.

 

[jsthntn247]

Alex Wheeler is the best in the country at timing a trigger. If it bothers you that much send it to him and I’m sure he will have it closing like butter. Look him up on the net or Facebook. Wheeler accuracy

 

[hereinaz]

Thanks, @bohem I would have followed up sooner, but I was on a hunting trip.

I don't have a single problem with the way you addressed me. I also don't have a single problem with my Nucleus. My short action runs flawlessly, and my long action is no different, though I don't have a barrel on it yet. I feel no need to send it to anyone or do anything with it based on the description.

I was trying to describe what I saw, and it appears that what I saw and what bohem described are the same thing. I intended to follow up and figure out how the mechanism worked and show what was happening. I may still do that. With your description, you saved me a ton of research and sifting through internet stuff.

 

[m6z]

It's also pretty darn beefy, weighing in at 4 lbs (64 ounces) compared to the 28 ounces of a Bighorn, the 32 ounces of a Lone Peak, or even the 56 ounces of an Impact Precision. The weight is a plus to me, since I want a heavy rifle anyways.

This can't be correct. The Nucleus is more than twice the weight of the Origin?

Edit: from ARC "Weight: Short action 2.1 lbs"

 

[ThePretzel]

This can't be correct. The Nucleus is more than twice the weight of the Origin?

Edit: from ARC "Weight: Short action 2.1 lbs"

https://www.americanrifle.com/product/nucleus-bolt-action/

Go to the specs, where it states that it's 4lbs. The 2.1 lb figure you're quoting is likely not including the bolt, rail, or recoil lug.

 

[Another Casual]

That's probably just the shipping weight. Main page for the action says:
"Weight: Short action 2.1 lbs. | Long action 2.4 lbs."

 

[Bradu]

https://www.americanrifle.com/product/nucleus-bolt-action/

Go to the specs, where it states that it's 4lbs. The 2.1 lb figure you're quoting is likely not including the bolt, rail, or recoil lug.

Guessing 4 lbs is the shipping weight. I can't see it weighing that.

 

[TexasTightwad]

I started communicating with ARC last week about this. I sent an email, got a call asking for clarification, then made and emailed a couple of videos to clarify. I'm sure giving me a call back has just slipped Ted's mind, and I have been too busy to remind him.

 

[308pirate]

Yup, same here... My excitement with my pre ordered John Hancock is all but gone. I’m new to this and don’t have the skill or even knowledge to have even figured this out if it was my rifle.

Perhaps, selling my spot might be the best option at this point

Jeez, overreact much?

 

[BLKWLFK9]

Jeez, overreact much?

right.. talk about first world problems.

 

[308pirate]

right.. talk about first world problems.

No shit. He's buying a complete rifle from a builder. Any problem he might have can be addressed by the builder.

It's not like he's putting his own together out of a box of parts.

 

[Rate_of_Twist]

No shit. He's buying a complete rifle from a builder. Any problem he might have can be addressed by the builder.

It's not like he's putting his own together out of a box of parts.

You’re right - just a bit too over paranoid on my part I guess.

First “custom” and most expensive firearm I will have purchased...

Admittedly- I’m probably just being a pain in the ass.

right.. talk about first world problems.

No shit. He's buying a complete rifle from a builder. Any problem he might have can be addressed by the builder.

It's not like he's putting his own together out of a box of parts.

Jeez, overreact much?

Funny how you complete omit my next two responses where I stated that I was over reacting....

Troll much?

 

[jsthntn247]

Before Ignition Timing

After Timing

 

[diverdon]

Yup, same here... My excitement with my pre ordered John Hancock is all but gone. I’m new to this and don’t have the skill or even knowledge to have even figured this out if it was my rifle.

Perhaps, selling my spot might be the best option at this point

I never knew a Lamborghini owner who claimed that his was completely free from mechanical issues yet I never heard one offer to trade for a new Chevy. I am somewhat confident that you will be happy if you take it and you will regret it if you do not.

 

[diverdon]

Too all the guys claiming the bolt is rough on closing, have you put any lube on the lugs? The first I put together is smooth as class. The amount of grease I use is nearly invisible, but who really wants metal on metal?

 

[JLP.Payette]

I never knew a Lamborghini owner who claimed that his was completely free from mechanical issues yet I never heard one offer to trade for a new Chevy. I am somewhat confident that you will be happy if you take it and you will regret it if you do not.

I agree. PVA will deliver a great product.

 

[jsthntn247]

Mine won’t eject cases. I disassembled it to clean the grease out and, wasn’t much there, and thought I might have put it back backwards. Does this look right.

 

[MarkLeupold]

Mine won’t eject cases. I disassembled it to clean the grease out and, wasn’t much there, and thought I might have put it back backwards. Does this look right.

Yes, that's backwards. The "wing" should be facing the inside of the action.

 

[JLP.Payette]

Mine won’t eject cases. I disassembled it to clean the grease out and, wasn’t much there, and thought I might have put it back backwards. Does this look right.

Pic from ARCS website.

 

[Skunkworx]

Is that just the photo or does the ejector look like it’s contacting the stock? Does it eject if you take it out of the stock?

 

[TexasTightwad]

Too all the guys claiming the bolt is rough on closing, have you put any lube on the lugs? The first I put together is smooth as class. The amount of grease I use is nearly invisible, but who really wants metal on metal?

There was grease on the lugs from the factory.

The response after my first email was quick, and I shot and sent some new videos to clarify what the issue was, but have not heard back. I sent another email to ARC last night, and am again waiting for a reply. It's been 9 days now

 

[atomic41]

There was grease on the lugs from the factory.

The response after my first email was quick, and I shot and sent some new videos to clarify what the issue was, but have not heard back. I sent another email to ARC last night, and am again waiting for a reply. It's been 9 days now

That is not cool. I'm waiting to see what happens with yours to decide what I do about mine.

 

[TexasTightwad]

Still no reply. I've been waiting 11 days now, and sent them a reminder 3 days ago.
Here are the videos I sent:

 

[diverdon]

Still no reply. I've been waiting 11 days now, and sent them a reminder 3 days ago.
Here are the videos I sent:

As nearly as I can tell from watching your videos there is nothing wrong with your action. I have one build into a rifle and when I or my Six or eight year old run it from behind the rifle it is very smooth. After watching your video I put the rifle on the bipod and stood off to the bolt side then moved it up and down. When you do it that way there is no forward pressure on the bolt so of course it does the same thing yours does. Who cares? Run it like a rifle and it will be fine. Ted is not well known for diplomacy so you might not want to hear his explanation.

 

[ThePretzel]

Watching those videos it's definitely more clear to me that the problem is you're not pushing forwards on the bolt when trying to close it.

See that angled cut-out that the bolt travels along at the very top of the action, directly behind the rail? You have to push forwards into that when cycling the action or it will feel clicky as you describe. When you're running the bolt you naturally push fowards on it and it feels super smooth. When you're just trying to push straight down on it from above, like in the video, it will feel notchy because you're not applying the forward pressure like you're supposed to.

 

[Skunkworx]

If he’s depressing the anti rotation pin enough for the bolt to start going down I’m going to say it’s not that.

When you pull that Calvin elite out (no trigger), does the hitch go away?

 

[TexasTightwad]

Watching those videos it's definitely more clear to me that the problem is you're not pushing forwards on the bolt when trying to close it.

See that angled cut-out that the bolt travels along at the very top of the action, directly behind the rail? You have to push forwards into that when cycling the action or it will feel clicky as you describe. When you're running the bolt you naturally push fowards on it and it feels super smooth. When you're just trying to push straight down on it from above, like in the video, it will feel notchy because you're not applying the forward pressure like you're supposed to.

As I've said before, you shouldn't have to jam it forward to close the bolt. The purpose of the lead-in angles (cams) on the lugs is to pull the bolt all the way forward into its final position. If I put a bunch of pressure toward the front while closing the bolt, the symptoms do go away. That's because the cams are never making contact, and the first time the lugs make contact is on the locking surfaces. So yeah, there's a workaround, but I shouldn't have to do that. The cams are not doing their job properly and I'm unwilling to accept that.

When I cycle the bolt on my Tikka, I can feel where the cams make contact, but it's not a "catch". The bolt smoothly rotates through, taking about the same amount of force as when it is contacting on the locking surfaces. Same thing on every other bolt-action I own. This is not how a quality action should behave. I wish I knew if that's just how all of the (Nucle... Nuclei?? ) are, but ARC won't answer my emails. And yes, I've been checking my spam folder too. I wasn't upset when I felt the catch and found the burrs on my bolt heads. I figured that no matter what, I'd end up with a good action because ARC would make it right. Well I'm starting to get mad now.

If he’s depressing the anti rotation pin enough for the bolt to start going down I’m going to say it’s not that.

When you pull that Calvin elite out (no trigger), does the hitch go away?

It sort of does. The reason is that when a trigger is in there, the trigger's sear holds the bolt's cocking piece from going forward. That means that the spring is trying to push the whole bolt backwards after the cocking piece is captured, meaning that the cams have to do some work to bring the bolt forward. With no trigger, the cocking piece never gets captured so there is no spring pressure pushing back on the bolt and there's nothing that the cams have to overcome. When you push the bolt forward while rotating, you are doing the cams' work for them, and when there's no trigger, there's no work to be done.

By the way, I do normally push forward while closing a bolt, but not as much as is required to completely skip over the cams.

 

[MilSpecOkie]

Savages have issues?

 

[whatsupdoc]

None of my bolt rifles do that, running them slow with minimal forward pressure causes no issues.
My nucleus build has not started yet waiting on a barrel so I will see how it behaves when finished.

I would be pissed if I bought a custom action and the manufacture did not respond to emails.

 

[TexasTightwad]

None of my bolt rifles do that, running them slow with minimal forward pressure causes no issues.
My nucleus build has not started yet waiting on a barrel so I will see how it behaves when finished.

I would be pissed if I bought a custom action and the manufacture did not respond to emails.

Yeah, I've been trying to get ARC to respond to emails for 2 weeks now. Nothing. So much for their warranty.

 

[character0]

@Jon_ARC not sure if you're aware of this thread. Might want to follow up.

 

[lash]

Yeah, I've been trying to get ARC to respond to emails for 2 weeks now. Nothing. So much for their warranty.

So I'm not taking the time to read through this mess again, but I have to ask if you have tried picking up the phone and calling ARC? It seems that most people have no trouble contacting them that way. Honestly, if I had an issue with a new product that seemed real, that is the likely first course of action I would take.

Let us know how a phone call works out.

 

[Praeger]

If he’s depressing the anti rotation pin enough for the bolt to start going down I’m going to say it’s not that.

When you pull that Calvin elite out (no trigger), does the hitch go away?

I'd start with Skunkworx' suggestion. If without the trigger the bolt closes smoothly, then it could be a trigger timing issue as the action is cocking on close. There is always a small amount of cocking on bolt close, but as the cocking piece is farther forward, the pressure you feel as the bolt is closed, is the resistance of the firing pin spring being compressed.

First, ensure there is no pin protrusion when cocked. Next check the firing pin protrusion with the firing pin released, it should be ~0.035".

 

[BLKWLFK9]

I called ARC a few weeks ago about a mag body breaking (probably my fault), and Jon answered after the 3rd ring. If you want to talk to someone, try the old fashioned way. Give them a holler.

 

[TexasTightwad]

The reasons I have been using email is that their warranty paperwork says to submit any warranty claims in writing, I was sending videos of the issue, and I like to communicate in writing on stuff like this.

@Praeger I have not measured firing pin protrusion, but I have checked for cocking on close from the back end. There is only .0045" of cocking going on, so the trigger timing is fine. I posted those measurements earlier:

Those videos were helpful. I seem to have a tiny bit of cocking on close.

Measuring the depth from the back of the bolt shroud to the face of firing pin head (the thing with the torx socket in the center of the back of the bolt) gives some insight as to what is going on. The bigger the depth measurement, the farther forward the cocking piece and firing pin are. It measures .040" with an open bolt, .0535" when rotated to the catch, .049" just past the catch, and .0545" with a closed bolt. The catch coincides with the cocking piece contacting the top sear of the trigger. After that, any changes in depth are because the bolt/bolt-shroud has moved while the cocking piece/firing pin has stayed still.

There is only .0045" of cocking on close. I really don't think that would be considered excessive or that you could blame the trigger. I think the issue lies in the locking lugs.

 

[Praeger]

The reasons I have been using email is that their warranty paperwork says to submit any warranty claims in writing, I was sending videos of the issue, and I like to communicate in writing on stuff like this.

@Praeger I have not measured firing pin protrusion, but I have checked for cocking on close from the back end. There is only .0045" of cocking going on, so the trigger timing is fine. I posted those measurements earlier:

Started on page 2 of the thread, my mistake.

Measuring from the back will show the relative distance the firing pin spring is being compressed beyond the point when the cocking piece contacts the cocking ramp (which is cocking on close), so if your measurements are correct that would take that off the table as a possible cause. However, you'll still need to measure firing pin protrusion to determine whether the firing pin's position relative to the cocking piece is correct. On the Nucleus, that adjustment is made at the front of the firing pin spring at the nut and flange. It is possible (though I don't think probable) that if the firing pin were grossly out of spec (excessive protrusion - or worse, protrusion after pin fall) you could potentially bind the firing pin spring which would cause greater resistance to locking/closing the bolt.

Your suspicion of the lugs causing the hitch would be corroborated by removing the trigger or the firing pin assembly. By removing compression of the firing pin from the equation, it would isolate the bolt lug/lug abutments as the probable cause.

Edit: I see you said you did remove the trigger and there is some of the hitch left. Given you've found burrs on the lugs, something is likely dragging at that point. I'd say it needs to go back to ARC.

 

[hereinaz]

I'm trying to figure out how to educate folks on this topic without coming across harsh or rude. THere is a propensity on here to talk about timing and trigger cock on close like it's a flaw in design. It seems to be a fundamental misunderstanding of how a bolt action receiver works and it keeps being dragged around forums as a complaint point. I think we need to at least talk about it to help folks understand because after reading a lot of this thread the misunderstanding about cocking force, cock on open, trigger timing, etc continues and the issues arise for all of us building rifles and working on receivers to keep customers educated and informed.


I'm not trying to single you out @hereinaz on purpose, your post is a perfect time to discuss what's going on in general with a bolt action receiver and the function of the mechanisms inside. Hopefully you won't take this as a slight as I'm not trying to, I'm just trying to explain how the stuff is functioning.

Cock on close is a design balance not an "issue", it's how actions work. Every action has a timing choice and it comes down to how a particular trigger fits in a receiver.
700's cock on close for 1/3 of the travel of the cocking piece. That's right, 35% of the cocking piece travel is done while closing the bolt.
Bighorn TL2's are ~15% cock on close
Bighorn TL3's are ~14% by design
Defiance Deviants are as well.


Mausingfields are 105% cock on open, -5% cock on close. AKA it overcocks on open by design.
That makes bolt lift heavier than it needs to be. It also means that the bolt closure feels like it snaps shut by itself because that's exactly what's happening.

The early GAP Tempest actions had massive overcocking on them, bolt lift was heavy but the bolt closure was actually assisted by the main spring itself and the effect was that it felt good to folks used to a 3 lug albeit with a heavy bolt lift... It also made the action feel faster even though it was less smooth.

Since the Nucleus is a 3 lug the split to put some cock on close exists to lighten bolt lift, again something that is a hot topic of debate around this forum.

The Seekins HAVAK action is 50/50. The bolt force is low on average but it feels odd because the bolt is constantly under a rotational restraint while opening and closing.

The trigger sear bar defines how much it is cock on close vs. cock on open.
There is a trigger made by timney designated as the "U" or extended sear.
It was developed in 2010 in conjunction with a now-defunct custom shop in Montana that brought the issue to Timney and went onsite to work with them. Lots of folks knew about it but those guys actually showed up and worked with Timney to get it into regular parts production.

The trigger manufacturers have different interactions with different actions. The individual triggers have as much to do with it as a design of an action does.

The governing equation to think about is the work being done.
If a bolt has a specific diameter and cocking stroke (let's use 0.7" nominal and standard 0.2" lift strokefor an apples to apples comparison) then the longer the angle a handle is rotated through for cocking the firing pin then the lighter the bolt force will be on average

Work = Force * Distance

Since the work involved is staying the same then the variables we're talking about are F and D. (There is probably a joke there, someone else can make it for me)

So, W is fixed.
We want F to decrease so therefore D must be as large as possible ((joke? that's what she said? nobody?))
Or if we want the shortest throw possible then the F will be large/hard (this seems like softballing in the setup here)

Nobody wants an action that has a 10 degree bolt throw but a 50lb bolt lift.
Conversely everyone wants a bolt we can open with 1 finger but we don't want to have a 180 degree throw to open it.
Everything is a balance.
In a 50/50 action we get that 180 degree throw. You have 90 deg to unlock and cock the bolt halfway, then another 90 to lock it and cock the other halfway. This is the lowest average force you'll get on bolt throw. Most folks don't like it though because we've been conditioned as shooters to have a light bolt closing stroke.

Now, there are safety aspects to it as well, but we can discuss those at a later time. Right now we're just talking about bolt lift vs. cocking piece timing.

You know how we say "Remington 700 CLone" and then the action doesn't quite fit the stock like it should? Same thing with triggers.
I just read somewhere on here that a guy stated "ARC Made the Nucleus footprint too close to a 700 to work with the lug lock on an MPA"

I just had to chuckle at that comment because it shows what people will accept in the industry as "close enough" and when someone actually makes a part that truly matches the thing it's supposed to clone a bunch of other stuff falls apart. Then another component that's "close enough" doesn't fit the company that made the original product to what the advertising states is a the bad guy.

@bohem ARC's website lists the Nucleus as 100% cock on opening. So, if that is correct, individual triggers may create a cock on close condition that could be addressed by a smith? Could loading of the spring increase the "hitch"?

I am not complaining, I have never had an issue running my short action Nucleus and it has performed flawless for me. Also, the long action Nucleus has felt just fine, next week I'll shoot it.

 

[Praeger]

@bohem ARC's website lists the Nucleus as 100% cock on opening. So, if that is correct, individual triggers may create a cock on close condition that could be addressed by a smith? Could loading of the spring increase the "hitch"?

I am not complaining, I have never had an issue running my short action Nucleus and it has performed flawless for me. Also, the long action Nucleus has felt just fine, next week I'll shoot it.

Can individual triggers create a partial cock on close condition? Yes. Depending where the trigger top sear engages/picks up the cocking piece, it may cause the firing pin to travel further rearward as the bolt is closed. Some custom actions offer trigger hangers which position the trigger top sear different distances from the cocking piece (usually in 0.010" increments) so the trigger can be timed to the desired level of cock on close.

 

[TexasTightwad]

Started on page 2 of the thread, my mistake.

Measuring from the back will show the relative distance the firing pin spring is being compressed beyond the point when the cocking piece contacts the cocking ramp (which is cocking on close), so if your measurements are correct that would take that off the table as a possible cause. However, you'll still need to measure firing pin protrusion to determine whether the firing pin's position relative to the cocking piece is correct. On the Nucleus, that adjustment is made at the front of the firing pin spring at the nut and flange. It is possible (though I don't think probable) that if the firing pin were grossly out of spec (excessive protrusion - or worse, protrusion after pin fall) you could potentially bind the firing pin spring which would cause greater resistance to locking/closing the bolt.

Your suspicion of the lugs causing the hitch would be corroborated by removing the trigger or the firing pin assembly. By removing compression of the firing pin from the equation, it would isolate the bolt lug/lug abutments as the probable cause.

Edit: I see you said you did remove the trigger and there is some of the hitch left. Given you've found burrs on the lugs, something is likely dragging at that point. I'd say it needs to go back to ARC.

Checked the firing pin protrusion. It is about .045" +-.005". Nothing out of the ordinary.

 

[308pirate]

The reasons I have been using email is that their warranty paperwork says to submit any warranty claims in writing.

That doesn't preclude verbal communications to discuss what has been submitted in writing/electronically. It's done in business all the time.

If you don't give them the courtesy of a phone call when they don't respond otherwise then it's hard to be sympathetic to your issue.

 

[Deleted member 10043]

All my Savages work like Savages. Don't think it be like it is, but it do. And what is up with the PC title change. Don't want to be offending anybody. Shit happens. And email is not considered in writing. Again, they don't think it be like it is, but they do. Change title to, "Nuclees, they don't think it be like it is, but it do." The problem is you guys talk each other into buying shit then submit your warranty claims here first. Put it into a box, mail it with a note inside.