Gunsmithing Truing action without recutting threads?

Jason280

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Dec 18, 2005
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I may have a lead on a Remington 700 5R .308 barrel for cheap, and I am considering using it for a 20" build on an extra action I have. Of course, I would like to have the action trued, but I realize that I would not be able to use the 5R barrel if the receiver threads need to be recut. Here's my question, how crucial is thread recutting to the truing process? Also, what percentage of 700 actions even need the threads to be recut?
 
Re: Truing action without recutting threads?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Jason280</div><div class="ubbcode-body">I may have a lead on a Remington 700 5R .308 barrel for cheap, and I am considering using it for a 20" build on an extra action I have. Of course, I would like to have the action trued, but I realize that I would not be able to use the 5R barrel if the receiver threads need to be recut. Here's my question, how crucial is thread recutting to the truing process? Also, what percentage of 700 actions even need the threads to be recut? </div></div>

You can have both. Have it squared and the chamber re-cut to match spec. win-win
 
Re: Truing action without recutting threads?

If I may:

Take a big step back and look at the big picture of what takes place when a gun goes "bang".

The fire control moves forward, the striker hits the primer which gets the powder lit. Pressure rises enough to get the case to swell out against the chamber. Then it continues to rise as the bullet starts traveling down the bore. Recoil now begins to develop (newtons little law) and pressure is still increasing. At some point in this the pressure will peak and start trickling down where it finally comes back to ambient atmospheric condition shortly after the bullet leaves the crown and makes its little journey ending in self destruction.

What I'm describing is essentially little more than a pressure vessel, but there's more to it. The bullet is going from zero to over 2x the speed of sound in a distance less than a meter. Think about that! It's also accelerating in rotation from zero to over a quarter million RPM (as with velocity, this varies based on twist rate, but it sounds more dramatic so go with it
smile.gif
)

We hear of terms like barrel whip, harmonics, frequency, amplitude, etc. I personally have a very laymans understanding of all these terms, but I am smart enough to know they are present, they are real, and they are significant.

Now consider that every one of these forces is managed/contained/transferred through the threaded joint between barrel and receiver. That fact in itself probably answers your question.

Harold Vaughn wrote a book years ago where he talked about this stuff at length. He illustrated the short comings of a 60* thread form. He demonstrated why its a poor choice for connecting a barrel to action. Using polarized light it conclusively showed how the joint is susceptible to movement.

Coming back to earth for a minute:

Something I marvel at is how well guns are capable of shooting. It tells me that we all must be doing "something" right. That being said it's important (in my mind) to not take stuff for granted. The threaded joint between barrel/receiver is (again in my opinion) the single most overlooked facet to accurate gunmaking in this entire industry. I poke that finger at 99.9% of people out there fiddling with these things.

Just take a moment to scroll through threads/posts regarding fitting a barrel. You'll see long winded dissertations about chambering, setups, work holding, and the selection of proper tools.

Very, very, very little is written about cutting well formed/fitted threads. The exception is often a noob getting his butt kicked over whether to set the compound at 29-1/2 degrees or 30*.

It's almost non existent.

I preach this stuff hard because I will go to my grave believing its just as important (maybe more) as all the other particulars.

How is a rifle going to shoot well if the barrel isn't pointing in the exact same spot each time. all the load development, bedding, chamber tricks, and/or shooter skill in the world won't correct this. How could it? If you can predict lightning strikes maybe then. . .

To answer your question I personally would insist on the threads being machined by someone who understands how to machine parts well. Your threads should be round, concentric and free of any taper, be it bell mouth, barrel, or whatever. They need to be bright in surface finish and as free of little burrs/inclusions as possible. This mitigates galling when the barrel is threaded into it. The barrel also needs to have bright shiny threads.

Here in lies the problem for most. It's intimidating to buzz a lathe up to sufficient RPM/surface speed where carbide tooling needs to run in order to produce the required surface finish, especially when the shoulder is there just begging for the insert to crash into it. (or a lug abutment in the case of a receiver). So we lumber along at 100-200 rpm and "ka chunk" our way through it just to get it done. Then we kratex the snot out of them so it appears we really did something.

We don't dare run the thread fit too tight for fear of it sticking (galling) We go one step further by slathering on a gravy layer of anti seize compound which is actually adding insult to injury in the case of a solid joint that won't move. (find a race engine builder that uses this stuff to install connecting rod bolts, head studs, etc- you won't as it prevents the flanks of the thread from "biting" one another to ensure the fastener doesn't come apart. On rod bolts they don't even use lock washers or lock tite! How the hell do they get away with that when it's holding something together that goes from zero to over 4500fpm and back to zero in a span of say 3-1/2 inches (piston speed/stroke)

CRAZY!

Just my two bits. Again, take with salt.

C.
 
Re: Truing action without recutting threads?

Jason, Im not going to comment on how crucial it is to recut the threads.
And..
I'd never encourage the remounting of a factory tube. New barrels are just too damn cheap. The barrel is the most important part on the rifle in my opinion and it happens to be the cheapest main component too.


If you really want another rifle to shoot and dont want to have it built around a new tube, then go ahead. Have a smith face the receiver, and remount the barrel safely.
It will shoot as good or better than a factory 5r and shouldn't cost more than $150-200 to do what you're asking.

It will probably shoot well under minute like most factory 5Rs do. But I'd just wait until I could afford to do it right.
 
Re: Truing action without recutting threads?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I'd never encourage the remounting of a factory tube. New barrels are just too damn cheap. The barrel is the most important part on the rifle in my opinion and it happens to be the cheapest main component too.</div></div>

Great point, for all the investment and down-time, do it right.
 
Re: Truing action without recutting threads?

if i just wanted to get a rifle together, and had an unmolested factory action and a free/cheap factory barrel, i'd toss them together and check the headspace. if i was lucky and it headspaced good, i'd shoot it. i personally wouldn't even worry about truing the action until i was ready to put a quality barrel on it.
 
Re: Truing action without recutting threads?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">Jason, Im not going to comment on how crucial it is to recut the threads.
And..
I'd never encourage the remounting of a factory tube. New barrels are just too damn cheap. The barrel is the most important part on the rifle in my opinion and it happens to be the cheapest main component too.


If you really want another rifle to shoot and dont want to have it built around a new tube, then go ahead. Have a smith face the receiver, and remount the barrel safely.
It will shoot as good or better than a factory 5r and shouldn't cost more than $150-200 to do what you're asking.

It will probably shoot well under minute like most factory 5Rs do. But I'd just wait until I could afford to do it right. </div></div>


i'd rather be shooting a factory barrel than not shooting at all. screwing on a factory barrel is much cheaper than what it would cost to purchase and fit a new match barrel. the time it takes to get a barrel blank in hand, the time it takes for it to be fit and the cost involved in both are not exactly what i'd consider cheap.


i also wouldn't touch the receiver face or any other part of the action if i was hoping to get lucky and have a factory barrel headspace correctly. my advice is to save the machine work on the action for when you are ready to go all the way.
 
Re: Truing action without recutting threads?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">Jason, Im not going to comment on how crucial it is to recut the threads.
And..
I'd never encourage the remounting of a factory tube. New barrels are just too damn cheap. The barrel is the most important part on the rifle in my opinion and it happens to be the cheapest main component too.


If you really want another rifle to shoot and dont want to have it built around a new tube, then go ahead. Have a smith face the receiver, and remount the barrel safely.
It will shoot as good or better than a factory 5r and shouldn't cost more than $150-200 to do what you're asking.

It will probably shoot well under minute like most factory 5Rs do. But I'd just wait until I could afford to do it right. </div></div>


i'd rather be shooting a factory barrel than not shooting at all. screwing on a factory barrel is much cheaper than what it would cost to purchase and fit a new match barrel. the time it takes to get a barrel blank in hand, the time it takes for it to be fit and the cost involved in both are not exactly what i'd consider cheap.


i also wouldn't touch the receiver face or any other part of the action if i was hoping to get lucky and have a factory barrel headspace correctly. my advice is to save the machine work on the action for when you are ready to go all the way. </div></div>

300,

From the words "extra action", you might assume he already has a rifle he's shooting.

And you cant just screw on a factory tube 90% of the time. Headspace and counterbore dimensions still need to be addressed. Even if you get "lucky" with headspace, those bolts/actions are so far off, there's a good chance the counterbore will give you trouble. The bolt could close, and measurements look ok with calipers, but you could still have either bolt nose contact, or too large of a gap which could be dangerous down the road if you ever blew a primer or case head.

I figure a gunsmith should look at it no matter what if a new barrel is going on. Doing a small set back like I was talking about would cost about $150 - $200 and ensure everything is good to go. Good chance it'd shoot too(as good as factory anyways).

 
Re: Truing action without recutting threads?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">And you cant just screw on a factory tube 90% of the time. Headspace and counterbore dimensions still need to be addressed. Even if you get "lucky" with headspace, those bolts/actions are so far off, there's a good chance the counterbore will give you trouble. The bolt could close, and measurements look ok with calipers, but you could still have either bolt nose contact, or too large of a gap which could be dangerous down the road if you ever blew a primer or case head.</div></div>

I must be really lucky.
I have done several factory rem barrel swaps and they were usually within 0.003" to 0.005" on headspace.
On most of them, I simply surface ground a lug to correct headspace. (it helps to have a box of old lugs to pick through and find an appropriate one to work with)
Remington leaves a lot more bolt nose and lug clearance than gunsmiths typically fit a gun so the guns I did the swaps on still had ample clearances.
Other ones needed to have a reamer run in about 0.002" to 0.004" as I could not find a lug thick enough to correct it that way.
 
Re: Truing action without recutting threads?

to address the OP's initial question, i think recutting the factory receiver threads would add the least amount of accuracy to the equation. i believe a receiver face that is square to the bolt raceway is most important. when i true a remington i never recut the receiver threads. i do square the receiver face, locking lugs, and true the back of the lugs on the bolt before lapping the bolt to the receiver. these rifles will generally shoot in the 1/4" neighborhood with a good custom barrel and i have yet to have one that wouldnt stay inside 1/2". in your case, if you are certain you will put a good quality barrel on it in the future go ahead and have the receiver trued, have the barrel setback and rechambered to headspace, and have it cut/crowned to your desired length. it should shoot pretty well. when the barrel is toast, you are ready for a good quality custom barrel.

chuck
 
Re: Truing action without recutting threads?

Chuck I agree with you and I bet the rifles built the way you described do shoot half inch or better.
We do cut the threads when we true because that is what's expected and thats what we promise to do for the price of a truing job. But if I had to pick one step to omit, it'd be cutting the threads. It matters, but like you said my guess would be it matters least.



There are dimensions you cant really measure for involving the counterbore if you dont start with a trued bolt.

Notice when youre truing a bolt how off the nose is? Hell how off <span style="font-weight: bold">everything </span> is.

Even if you throw your calipers on the nose and it reads say .690. Just because the counterbore diameter is .700-.710, doesnt automatically mean you have .005 to .010" all around. You could have a huge gap on one side and the other side touching.

If Remington uses larger than a .010" gap for counterbore dimensions thats fine for them. I've been taught .010" should be max. I wont screw a gun together that isnt "right", as I believe it to be.


Will the rifle fire and not blow up if counterbore dimensions are off, sure. But is it right?


How big of a gap do you guys feel is safe and acceptable for counterbore dimensions?


In school I played with taking a bolt from one rifle and gently trying it in other rifles. Most of the time headspace was off.
I replaced a bolt in one rifle with another factory bolt. Not only was headspace off by about .010" but the counterbore dimensions were way off. Bolt wouldnt even close without any gauge or case in at all. Just because of one of the counterbore dimensions(it was tenon length).


 
Re: Truing action without recutting threads?

The counterbore doesn't do a dern thing.

If it did the Nesika hunter/repeater actions would have them. So would Winchester P/F, Savage, etc. . .

Three rings of steel is a marketing ploy from the 1960's.

At best it's an initial "kinda sorta" feed ramp for the cartridge.

At worst it's a pinch point for foreign material, grossly out of alignment bolt bodies, and a feature that will focus searing hot/high velocity gasses right down the raceway towards your mug in the event of a violent case rupture.

C.
 
Re: Truing action without recutting threads?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">How big of a gap do you guys feel is safe and acceptable for counterbore dimensions?


</div></div>

i'd feel safe without a counterbore at all. many actions don't include that feature.

it's there so i include the feature but by no means do i feel it is necessary.
 
Re: Truing action without recutting threads?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">And you cant just screw on a factory tube 90% of the time. </div></div>

how many of them have you tried to come up with that percentage?
 
Re: Truing action without recutting threads?

Randall you say you must be really lucky, yet you say the headspace dimension is normally within .003" to .005"?? And you pick the right size lug from a box of different size lugs. That doesn't sound like they're all swappable to me. Sounds like youre correcting headspace with different lugs and a surface grinder, and no mention of counterbore..
Im sure theyre fine and most probably shoot acceptably but just the look of a Remy action and barrel tenon when its first taken apart looks unacceptable. Taking measurements or watching one get trued confirms it looks like it is. I dont think we'd agree to screw a barrel on to a rifle without a certain amount of work by us.



I know counterbore doesn't effect accuracy. Just safety.
Those actions without counterbores have other design characteristics that are designed to make it safer.
If it doesn't have an action ring like the Mausers, I think the barrel counterbore for the bolt nose is necessary. Mausers internal action rings plays the same role. Is that not why Remington, the two lug Mauser wana-be included it in the first place? Its been that way long enough I'll stick with it.
I kinda like Mauser actions now actually.

And I think exercising some standardization concerning counterbore is the professional thing to do. That is why I wouldn't ever screw on a factory barrel for someone, and only check it with calipers and a go gauge.

I wouldn't screw the barrel on unless I was allowed to do minor truing work, and set back the barrel.

Without truing and set back there are things I couldn't be certain of.

Factory tubes, once taken off the rifle is was sold on, should be used as something other than a rifle barrel IMO



Putting an untouched factory tube on another untouched factory action/bolt, is no different than taking 20 rifles, mixing up all their bolts, and putting the bolts randomly back in to the rifles and thinking everything is ok if the bolt closes on a go gauge.



I gave my opinion on the OPs question. Im not going to debate how important or unimportant the counterbore is.
 
Re: Truing action without recutting threads?

so keith, do you really think that remington creates a barrel counterbore/tenon length/chamber depth/recoil lug thickness specific to each individual action? or do you think that it may be faster/cheaper for a manufacture putting out lots of product to have looser tolerances than a custom rifle builder but still allow components to work together safely?
 
Re: Truing action without recutting threads?


They may put them out with looser tolerances, but I dont think they grab parts from a big box and screw em together. I think a little gunsmithing is involved. Maybe the barrels are short chambered/ short counterbored, and a guy finish chambers it and sets counterbore dimensions mating it up to a serialized action/bolt pair... I have no idea.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">"if i just wanted to get a rifle together, and had an unmolested factory action and a free/cheap factory barrel, i'd toss them together and check the headspace. if i was lucky and it headspaced good, i'd shoot it"</div></div>
Again, no different than throwing some random bolt into your rifle and simply checking headspace real quick.
Ya it might be fine but why do it for yourself and why do it for someone else?

I cant believe youre even arguing against the minimal work it takes to face an action and set the barrel back one turn. Truing the two bolt nose surfaces wouldn't take much time either and would help with a nice consistent counterbore.

If a guy is putting a rifle together like this, I think its worth $200 to him to have it done right, and have a chance at accuracy being improved.

If a complete rebuild is done recutting every surface like SAC does, I think the rifle will shoot superbly. It would be like a custom build with a factory bore. Probably shoot half MOA.
The only reason I dont think we'll really be offering it is we'd rather see it done with a new barrel. Shilen match barrels are in the $250 range and will shoot great. Half MOA... as good as the smith built the rifle.
 
Re: Truing action without recutting threads?

Be careful truing the bolt nose face. It serves no purpose other than looking nice and clean. The end of the bolt nose is real thin. Removing metal is not a good thing because it weakens the end of the bolt nose which can lead to the extractor ripping out of the end of the bolt.

Rip the extractor out and then you will either have to repalce the bolt or bush the bolt nose and install a Sako type or M-16 extractor.
 
Re: Truing action without recutting threads?

Good point. With the bolt nose, we dont remove material until its cleaned up completely like most surfaces UNLESS, it cleans up in only a couple thou. We make as small of a cut as we can until it's somewhere between 70% and 85% better than it was if its off a lot. Know what I mean where you watch the moon turn into a circle... removing only a couple thou

The same goes for the outside of the bolt nose, and the bolt diameter when touching before the lugs. Only the lugs front, sides, and back are getting trued 100% no matter how much material needs removing(within reason of course).

The reason we true the nose is the counterbore. So we can try to have a nice even gap all the way around. .010" being the goal.
 
Re: Truing action without recutting threads?

Maybe this will shed a little light on this.

Before us is an action I'm in the process of truing. The centerline of the receiver has been indicated to a true position of .001" (anyone who knows what this really means understands that in the X/Y/Z axis this part is now indicated essentially to within .00033" of theoretical zero. You take the .001 and / by 3 since we live in a 3 dimensional world.

What I'm saying is this thing is pretty much nutz on for center. It's been aligned with the spindle of my CNC mill to within .00025" over a 7" span. Again, it's perty dern straight.

Now, look closely at the photo. What do you see? If we call the base holes 12 o clock and go around the thing accordingly we notice that bluing remains starting at roughly 7:30 and ending around 10:30.

Keep in mind I punch receivers to a new thread dimension. I don't just "go till it cleans up" 1.085X16 is the pitch I use. 1.085" is .0225" larger than 1-1/16. That's .01125" per side.

Over ten thousanths yet the threading tool/boring tool hasn't even touched the existing thread.

Anyone here reeeeeeaaaaaalllllllllyyyyyyyy want to screw an action onto a brand new barrel with a receiver bore out of whack that far?

Keep in mind, that's the MINIMUM its out. Since the tool hasn't cut anything and my thread plug gauge checks out on what I have machined, I have no real idea of knowing just how far I'll have to go to fix this. Keep in mind it NEEDS fixin as that portion of the receiver basically won't support the barrel. What I'll have to do is just keep going till she squeeks in. Since I'm barreling it, it's of little consequence. I'll just adjust my tennon program accordingly.

Pain in the butt, but not a show stopper.

There ARE reasons why we do this stuff germs.

Have a great morning.

C.

DSC_0042-2.jpg


DSC_0041-2.jpg
 
Re: Truing action without recutting threads?

Using cutter compensation as my "gauge" I've had to go an additional .0105" to get rid of it.

So it's looking like this biche was somewhere between .015 and .020 off center.

I think that kinda puts into perspective why this is never a bad practice to have done-so long as the person doing it knows what the hell they are doing mind you. . .

I have to wonder if a tap mounted on a stick crammed in the receiver would have resolved this issue. My gut says "no".

DSC_0044-2.jpg


DSC_0043-2.jpg



C.
 
Re: Truing action without recutting threads?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">I have to wonder if a tap mounted on a stick crammed in the receiver would have resolved this issue.</div></div>

Don't get me started on that...
 
Re: Truing action without recutting threads?


Mr. Dixon,
Very impressive all around. While I generally just shoot rifles and leave the real work to the professionals I am always impressed with a machinist's creativity with fixtures and setups. It seems you guys always find the best way to take a tough task and make it simple. This brings me to my question. What method do you use to align with the bolt bore while chucked on the o.d. of the action?

Thanks in advance,
Wade



<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: C. Dixon</div><div class="ubbcode-body">Using cutter compensation as my "gauge I've had to go an additional .0105" to get rid of it.

So it's looking like this biche was somewhere between .015 and .020 off center.

I think that kinda puts into perspective why this is never a bad practice to have done-so long as the person doing it knows what the hell they are doing mind you. . .

I have to wonder if a tap mounted on a stick crammed in the receiver would have resolved this issue. My gut says "no".

DSC_0044-2.jpg


DSC_0043-2.jpg



C. </div></div>
 
Re: Truing action without recutting threads?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wade</div><div class="ubbcode-body">
Mr. Dixon,
Very impressive all around. While I generally just shoot rifles and leave the real work to the professionals I am always impressed with a machinist's creativity with fixtures and setups. It seems you guys always find the best way to take a tough task and make it simple. This brings me to my question. What method do you use to align with the bolt bore while chucked on the o.d. of the action?

Thanks in advance,
Wade</div></div>

He shows his setup here. Pretty slick setup that I may have to copy.
 
Re: Truing action without recutting threads?

I spent a week at Illion a few years back working in the repair section and touring the factory with Lyle and the guys from the LE Training group. So I got a VIP factory tour which really opened my eyes to a lot of things.

Here's how the chambering at Remington went. Rifles come out short chambered with the caliber already stamped on the barreled action. There is a wall of reamers on "T" handles all marked with calibers and headspace gauges on the wall and an air drill with some 400 gt. The worker grabs a barreled action, the "T" handled reamer and literally reams it by hand, then blows the chips out, does a go, no-go check and adjusts if needed. Then he polishes the chamber for a second and viola there's your new factory Remington 700. It didn't look like any of the reamers were piloted and I'll bet they don't change them out as often as we think.

IMO this method is the reason so many brand new factory belted mags won't unlock after firing or have so much difficulty closing. Honestly, I'm amazed at how many factory guns do shoot well which probably has as much to do with modern optics as anything.
 
Re: Truing action without recutting threads?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: angelballer</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wade</div><div class="ubbcode-body">
Mr. Dixon,
Very impressive all around. While I generally just shoot rifles and leave the real work to the professionals I am always impressed with a machinist's creativity with fixtures and setups. It seems you guys always find the best way to take a tough task and make it simple. This brings me to my question. What method do you use to align with the bolt bore while chucked on the o.d. of the action?

Thanks in advance,
Wade</div></div>

He shows his setup here. Pretty slick setup that I may have to copy. </div></div>



Thanks. For the record: Good machinists are just kids who could never shake the tinker toys.
smile.gif
 
Re: Truing action without recutting threads?


Thanks for the link. That is very impressive.



<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: angelballer</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Wade</div><div class="ubbcode-body">
Mr. Dixon,
Very impressive all around. While I generally just shoot rifles and leave the real work to the professionals I am always impressed with a machinist's creativity with fixtures and setups. It seems you guys always find the best way to take a tough task and make it simple. This brings me to my question. What method do you use to align with the bolt bore while chucked on the o.d. of the action?

Thanks in advance,
Wade</div></div>

He shows his setup here. Pretty slick setup that I may have to copy. </div></div>