increasing headspace on newly installed factory original fixed shouldered barrel

[R. Cram]

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?

that is the challenge in putting a barrel on ,to minimize headspace and have minimal clearance from bolt face to barrel but then you go to a tapered cone fit like a pre 64 win. and there is more unsupported cartridge case in the rear of the chamber than can be achieved with non tapered styles and work just fine. I agree a person should verify this clearance if shimming the barrel to make sure it is not excessive

 

[RuninL8]

No, I'm saying that a shim moves the barrel in exactly the same way that a Savage barrel is moved by threading it in or out before locking it in place with the nut. Both the head-space and the bolt to barrel gap are effected identically. The same it true if substituting a thicker or thinner recoil lug (were this not a Howa).

Yes, but that savage barrel may will be chambered that extra .005 deeper for the headspace to be correct when you go to tighten it down. Even though you move the effective headspace by moving the barrel the actual chamber is head spaced to give you a safe rifle. I have personally built (chambered on my lathe in my shop) a few hundred rifles and I would never let one go out .005 incorrect. What would insurance say if something bad happened, I can't take that risk. I honestly could not tell you if that .005 will matter or not, but a case that has an extra .005 not supported is not worth the $100 dollars it would take to fix the issue.

 

[aschler]

Yes, but that savage barrel may will be chambered that extra .005 deeper for the headspace to be correct when you go to tighten it down.

It would be interesting to know how close the bolt to barrel gaps are for prefit barrels that use barrel nuts actually are in practice. I remember seeing some polls on this site about headspacing Savage rifles and though I don't remember the exact numbers a pretty good percentage of people didn't even use a go gauge so I doubt the tolerance on that dimension is particularly tight. I've also never seen it recommened to check this dimension when installing a new barrel.

 

[aschler]

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.

The shim will conform to that degree of misalignment; there is a point it won't be able to but you wouldn't want to screw that barrel into that action. If the shim was significantly thicker you also might get some none uniform loading.

You wouldn't want to heat treat the shim, all the loading is compressive and it is already strong enough not to suffer any damage.

 

[aschler]

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?

The OP originally didn't say they handload, it has been suggested and I don't think the OP has ever said if they handload or not. Even if they do, they may want to keep the gun at SAAMI specs.

My pushback against the anti-shimming crowd seems to have fueled most the debate but I actually like osok-k1's suggestion to lap the bolt lugs the best.

 

[RuninL8]

It would be interesting to know how close the bolt to barrel gaps are for prefit barrels that use barrel nuts actually are in practice. I remember seeing some polls on this site about headspacing Savage rifles and though I don't remember the exact numbers a pretty good percentage of people didn't even use a go gauge so I doubt the tolerance on that dimension is particularly tight. I've also never seen it recommened to check this dimension when installing a new barrel.

It would be interesting to find out on a factory pre-fit.

 

[SSgt G Cody]

Remington built "Three Rings of Steel" around that spot for safety reasons; Now you want a sheet-metal shim there? A shim is much thinner and weaker than any recoil lug. Most lugs are about 1/8" (.125") thick, not a flimsy .005" thick. Then factor in surface tension, hardness, crushability, and torsion, and the shim is weak in all of these, and obviously the poorer choice. Tool Steel Strength is safety.

 

[Luckyshot7]

Remington built "Three Rings of Steel" around that spot for safety reasons; Now you want a sheet-metal shim there? A shim is much thinner and weaker than any recoil lug. Most lugs are about 1/8" (.125") thick, not a flimsy .005" thick. Then factor in surface tension, hardness, crushability, and torsion, and the shim is weak in all of these, and obviously the poorer choice. Tool Steel Strength is safety.

I watched a gentleman shoot a stage with his 6.5PRC barrel loose. We could not figure out why his shots were going wild, until he grabbed the barrel and twisted it off by hand...

He did not blow up

 

[aschler]

Remington built "Three Rings of Steel" around that spot for safety reasons; Now you want a sheet-metal shim there? A shim is much thinner and weaker than any recoil lug. Most lugs are about 1/8" (.125") thick, not a flimsy .005" thick. Then factor in surface tension, hardness, crushability, and torsion, and the shim is weak in all of these, and obviously the poorer choice. Tool Steel Strength is safety.

The shim will only see a compressive load between the action and barrel and it will handle that load quite easily.

 

[Rocketeer77]

That 60,000 psi is sealed by the barrel steel the shim only has the pressure of how tight the barrel is torqued to.

You now have two potential leakage areas, you also assume 100% perfect alignment with zero gaps. The brass hopefully seals everything up nicely and then you'll be OK. Shims don't like being pounded BTW personally it's a dodgy fix! Machinist opinion here, everything stretches when you fire that round.

 

[Rocketeer77]

I watched a gentleman shoot a stage with his 6.5PRC barrel loose. We could not figure out why his shots were going wild, until he grabbed the barrel and twisted it off by hand...

He did not blow up

It's called luck

 

[Rocketeer77]

Whole lotta knee jerk reactions every time someone does something a bit different without stopping and thinking a minute about what is actually happening.

The shim isn't a gasket. It's not holding pressure back. It's a spacer. If you continued the thread out further on the barrel shank and added an adjustable barrel nut, you would be doing the same thing. Moving the barrel/chamber shoulder datum point away from the bolt face to adjust the headspace. Barrel nuts do not blow up or blow off due to pressure. Why would a shim?
Torque on the barrel to the receiver makes no difference on the ability to contain pressure. You can use a barrel nut style barrel, with no nut. Screw it in and set the headspace to a go gauge , and shoot it with the barrel just sitting in the receiver. It's not going to blow up. It's not gonna rocket off downrange. Torque (to a shoulder or with a barrel nut) just gives you a repeatable index and assures the barrel doesn't loosen over time and use.
Yes, you have to look and make sure you do not move the barrel out so far you have too much unsupported brass at the bolt face. But the amounts of adjustment we are talking here will not do that. Again, you could do the same with a barrel nut install.
Go back through this thread and count how many quality information posts are in here. Not trying to single out anyone but stop and think a minute before typing. Yes, discussion is good and educational but read and think please. Just for a minute.

The barrel nut certainly isn't under any major stress, when you fire a round the barrel goes one way the action the other way, so 100% where the shims located it opens minutely as the surrounding steel stretches slightly (elastic zone) this is basic engineering 101 stuff. The best quality rifles have their barrels screwed hard into the action everything perfectly spaced and aligned. Nuts and shims to achieve the correct headspace are simply shortcuts for poor/cheap manufacturing quality, it's also why I own Sako rifles. This is an experienced engineering opinion here not an armchair expert.

 

[aschler]

You now have two potential leakage areas, you also assume 100% perfect alignment with zero gaps. The brass hopefully seals everything up nicely and then you'll be OK. Shims don't like being pounded BTW personally it's a dodgy fix! Machinist opinion here, everything stretches when you fire that round.

If you have gas blowing past your recoil lug a shim wedged between it and the barrel are the least of your problems.

 

[Black Hat]

I watched a gentleman shoot a stage with his 6.5PRC barrel loose. We could not figure out why his shots were going wild, until he grabbed the barrel and twisted it off by hand...

He did not blow up

I shot F Standard with a bloke for about 9 years that used to unscrew his barrel by hand before coming off the mound, and he shot well!