increasing headspace on newly installed factory original fixed shouldered barrel

[aschler]

Either way. Shims don't belong between a barrel and action. If I hand a client a barrel with a shim. I'll never see a rifle job ever again. Granted seems to be a personal gun. Still gotta have standards.

That is an excellent reason for you not to use shims in rifles you build for someone else.

I design seed processing facilities; many the the chemicals we put on the seed and several of the operations we do are purely cosmetic. I understand some farmers are going to get upset if they recieve a $300+ bag of seed that doesn't look perfect but I wouldn't put those chemicals on or perform those operations if I was producing that seed for myself.

 

[R. Cram]

if you reload cut off a die by .005 and and that will allow the brass to fit the chamber also check some factory loads and see if they will chamber with a short by .005 chamber or better yet take off .005 on a shell holder and it might be usefull in the future put some blue on the face of the bolt to make sure it doesn't hit the back of the barrel

 

[MagnumManiac]

You would want a 0.006" thick shim or a 0.007" thick shim if you want to error on the side of caution.

Actually, you wouldn't want a shim…EVER.

Cheers.

 

[ntsqd]

I get people not wanting a shim in their own rifles or especially in a rifle that they've built for a customer. But if a guy wants to shim the barrel to set the headspace, and it doesn't create a safety problem, then I can't think of a valid reason why he can't or shouldn't do it.

It is not how I would do it for a rifle that I take pride in, but if I'm testing something odd and it's safe then I wouldn't have a problem with shooting it. Just because it is rarely if ever done that way doesn't mean that it's not a reasonable way to do it.

And I'm going to point this out; how many here have used peel-washers to time an AR's flash-hider? How many (I'm dating myself here) have mounted a scope using Buehler scope rings? How many have tightened up a Ruger Mk. series .22LR pistol's trigger group with an early Volquartsen kit? How about installing an Aero M5 hand guard? All of those use shims, so it's not like firearms have never had a shim in them anywhere.

I know that it goes against the grain for most, but can anyone think of a valid reason, a safety issue or some good reason why not to? Facts, not opinions, are what I'm interested in.

 

[MagnumManiac]

Facts, if it was correct, which it isn't, then why isn't everyone doing it?
Just because it MAY work doesn't mean it should be…

Cheers.

 

[Darryle]

And I'm going to point this out; how many here have used peel-washers to time an AR's flash-hider?

The flash hider doesn't touch the bullet in that scenario.

My brain is giving me this scenario and it is most likely wrong, it's my brain after all.

Think of the face of the action as a clock, say this face is .001" proud at 6, barrel is proud .001" out at 3 and shim is perfectly parallel. In my brain, I going to bottom out at those 2 surfaces early, pushing the muzzle away, right and up in our scenario. The tension is located in those two areas, over time, the potential of failure of the shim is highest there because of crush and the harmonic oscillation during firing.

Now, you say, but, but, but, thicker recoil lug and such, a shim has no where the load capability of a precision ground recoil lug, it's impossible to heat treat a shim that thin to the same degree as a recoil lug, at least to my knowledge.

They also make shims and people shim AR barrels all the time, yes they do, but I don't and it's because I don't want one more point of potential failure. Either I swap receivers or barrels or both or replace the barrel extension, but never a shim.

 

[Hugnot]

As mentioned - get a finish reamer & hand turn it make the chamber deeper using chamber gauges..

The units commonly applied for barrel torque are ft-pounds, not psi.

 

[ntsqd]

To be clear I'm not saying that using a shim doesn't have it's downsides, I mentioned my own concerns in my first or second post about it. A shim is an easy way to get to a desired position and maintain it. In firearms we don't usually see them not because they can't be used here, but because the Art of the building of firearms demands a more esthetic solution.

What I am saying is that if it doesn't create an unsafe condition then functionally how is a .005" thick shim any different from a .005" thicker recoil lug? (Yes, I know that we're specifically dealing with an action that has an integral recoil lug.) Set aside any revulsion the idea generates and look at the idea from a purely mechanical perspective. I've also said that I don't particularly want a shim in any of my own rifles, but that this is a personal choice on my part and not because there is a functional problem with the idea. I am open to using a shim to test a theory or to find out what a final dimension of some part should be.

When Savage first introduced the barrel nut all of these same arguments were made against them too. Now the barrel nut is more or less an accepted solution. Some will not ever own a barrel nut rifle. They find the idea abhorrent and that's fine, it is their choice. Others have no problem with them and are having a blast assembling rifles that employ them to their advantage. FWIW there is such a thing as a "Howage" barrel nut. McGowen, for one, makes the nuts and offers barrels to do this.

My goal in taking this position isn't to convince everyone to start using shims to do everything. I'm just trying to get people to look at them objectively and realize that in certain situations they are another tool in the box that can be used, permanently or temporarily, to achieve a desired result.

 

[ntsqd]

None of the recoil lugs, or for that matter, actions, that I have worked with are terribly hard. A lot of discussion talks about being careful to not heat these parts hot enough to hurt the heat-treating, but while I've no doubt that they have been heat-treated they aren't very hard either. (Given the use I see this as a good thing!) Having worked with shim stock for decades the thought that a typically stainless steel shim is going to be significantly more ductile or compressible than the action (& separate recoil lug if present) is a preposterous one. We are not talking about a copper or aluminum crush washer which do intentionally behave in the suggested manner.

Given the size of tenon threads I do not believe the torque used to install barrels is anywhere near the max torque that these threads could be torqued to. Even those that require cutting the shoulder as the only way to get them loose likely aren't as tight as is theoretically possible. 100 ft-lbs of torque on a Ø1.062" barrel tenon is roughly 5700 lbf of compressive force. Assuming a Ø1.25" OD that's an area of .341 sq-in which means that the compressive pressure on the shim is roughly 16,570 psi. 18-8 Stainless is one of the more common metals that shims are made from and it has a Yield Strength of 31,200 psi.

What this is telling me is that a barrel installed with a torque that few will ever attempt results in a compressive force that is about half of the yield strength of the metal a shim would be made from.

 

[Black Hat]

if you reload cut off a die by .005 and and that will allow the brass to fit the chamber also check some factory loads and see if they will chamber with a short by .005 chamber or better yet take off .005 on a shell holder and it might be usefull in the future put some blue on the face of the bolt to make sure it doesn't hit the back of the barrel

The above, is exactly what I would do.

I shimmed a bolt for a Savage 93R17 once. It worked and closed the headspace, I might add it was going in the creek if it didn't work, but I would never try this on a centrefire.

 

[RuninL8]

For everyone against shimming, how is it different than using a thicker recoil lug in actions that allow it?

Because, when you use a thicker recoil lug you allow for that in the headspace itself, simply use a shim is not actually changing the headspace, you are changing the bolt face/nose clearance and they are 2 separate things. Any increased clearance here can possibly produce a dangerous situation, because you have no idea what the start clearance is. For my builds I like to see no more than .008 clearance for hunting rifles. If your rifle is already to that point now you are at .013. Can that create a problem maybe, maybe not. Worth your face?

 

[FEENIX]

Because, when you use a thicker recoil lug you allow for that in the headspace itself, simply use a shim is not actually changing the headspace, you are changing the bolt face/nose clearance and they are 2 separate things. Any increased clearance here can possibly produce a dangerous situation, because you have no idea what the start clearance is. For my builds I like to see no more than .008 clearance for hunting rifles. If your rifle is already to that point now you are at .013. Can that create a problem maybe, maybe not. Worth your face?

Agreed! I do not believe in taking unnecessary risks, especially when things can go KABOOM! Fix it right, correctly, and be done with it.

 

[ntsqd]

Because, when you use a thicker recoil lug you allow for that in the headspace itself, simply use a shim is not actually changing the headspace, you are changing the bolt face/nose clearance and they are 2 separate things. Any increased clearance here can possibly produce a dangerous situation, because you have no idea what the start clearance is. For my builds I like to see no more than .008 clearance for hunting rifles. If your rifle is already to that point now you are at .013. Can that create a problem maybe, maybe not. Worth your face?

Same argument could be made against barrel nuts. I think experience has proven that such an argument will fail.

 

[Ken61]

Got bogged down in the shimming discussion, didn't read everything.
Why not take a little off the shellholder, bump the shoulder back and go shooting?