Go gauge for shouldered prefit?

[FrogFire7]

I would think you should be able to take the barrel to a gun smith with the appropriate lathes that can bump the shoulder, adjust the threading etc to fit the barrel to the action.

Barrel can be set back, but it will require a lathe. I have used virgin brass before when there was not a headspace gauge to be found, but it is not the best way. If the brass fits, add a piece of scotch tape to the base and try it. The tape usually runs about .0025-.003. Problem is, I have seen "match" brass vary as much as .002 to .003 in the same box. Measure the tape if you use it, I have seen some of it run almost .005.

Yes, it can definitely be set back by a gunsmith. However that completely negates all the benefits of a prefit shouldered barrel, in my opinion. If you wanted a gunsmith to fit the barrel you would have been better off buying a blank and paying for the labor to start with.

 

[clemens]

Myself bit leary of the tape trick, How true is it that one can get a crush factor with tape?

 

[Taj]

Myself bit leary of the tape trick, How true is it that one can get a crush factor with tape?

Yeah, you can't force it. It does work in a pinch. I have also seen a few factory guns that will close on a No-Go. That's why we have field gauges. As long as it won't close on a field gauge the gun is usually safe. I have also seen No-Go gauges that are under SAAMI max specs. Many gauge makers will tell you up front that their NO-Go gauges are under SAAMI max.

 

[Joel Russo]

Tagging in for entertainment.

 

[quandary]

Yes, it can definitely be set back by a gunsmith. However that completely negates all the benefits of a prefit shouldered barrel, in my opinion. If you wanted a gunsmith to fit the barrel you would have been better off buying a blank and paying for the labor to start with.

Of course thats the case. The question however was not whether you would want to do that. The question was why check with go/no-go gauges you can't do anything about it. My point was that you can in fact do something about it. The other solution is to send it back to the who ever reamed it and wait 6 months.

 

[pavementends]

One can definitely set head space too tight either by "crushing" the tape or by using a nogo gauge that is under saami specs. which can result in a condition where some factory ammo will not chamber. If one is loading for a cartridge for which there is no factory ammunition the question becomes one of matching your chamber and dies.

 

[bigngreen]

Go Guage and tape works, I use go Guage and .001 brass shim. The issue with using the brass is until you fire a few you don't know if your undersize for your dies thus not seeing any sizing when you need it.

 

[nksmfamjp]

Here's another way to look at the subject. Let's say you wanted a gunsmith to build your rifle. Would you expect the smith to use gauges, or just fudge it and hand you the rifle?

Let's say you built this rifle and it wasn't to your liking and you wanted to sell it. On the ad you fully disclose you didn't use gauges when building the rifle. How many people do you think you'd turn away from the sale?

How many gunsmiths use a GO gage and shims and don't tell you about it as the buyer. It is within the gunsmiths responsibility to get it right. It is not a requirement to tell/teach the buyer how it was built.

 

[MagnumManiac]

This is the most overthunked thread I have ever seen on here.
A pre-fit for a PARTICULAR ACTION is a finished fitted product.
It requires no gunsmithing, it simply screws on and headspace and timing are done. Each barrel should be within SAAMI tolerances when CNC turned/threaded/chambered.
The only time you need go/no-go gauges is when you are cutting chambers.

Cheers.

 

[nksmfamjp]

One can definitely set head space too tight either by "crushing" the tape or by using a nogo gauge that is under saami specs. which can result in a condition where some factory ammo will not chamber. If one is loading for a cartridge for which there is no factory ammunition the question becomes one of matching your chamber and dies.

Huh? I get that SAAMI min can be just a smidge too tight, but how am I compressing tape to a negative interference. The tape is to ensure a loose, but almost min spec chamber. Hell, put 2 pieces on there….or foil.

 

[Rob01]

This is the most overthunked thread I have ever seen on here.
A pre-fit for a PARTICULAR ACTION is a finished fitted product.
It requires no gunsmithing, it simply screws on and headspace and timing are done. Each barrel should be within SAAMI tolerances when CNC turned/threaded/chambered.
The only time you need go/no-go gauges is when you are cutting chambers.

Cheers.

AMEN! Guy saying you will be killed doing this really gave me a chuckle. Seems like a lot are confusing barrel nut prefits and shouldered prefits too.

 

[FireFlyFishing]

How many gunsmiths use a GO gage and shims and don't tell you about it as the buyer. It is within the gunsmiths responsibility to get it right. It is not a requirement to tell/teach the buyer how it was built.

Let's say I didn't have the means to put together a prefit, so I took it to a smith to ensure the job was done properly. I interview the smith if they use gauges. If the smith wouldn't tell me or they said "no, I use a case and scotch tape," I'd be taking my rifle elsewhere. What would you do?

This is another reason I'm loath to buy "custom" rifles off the classifieds. I have no idea how the rifle was built.

 

[Taj]

This is the most overthunked thread I have ever seen on here.
A pre-fit for a PARTICULAR ACTION is a finished fitted product.
It requires no gunsmithing, it simply screws on and headspace and timing are done. Each barrel should be within SAAMI tolerances when CNC turned/threaded/chambered.
The only time you need go/no-go gauges is when you are cutting chambers.

Cheers.

You said the magic words "should be". In 50 years as a gunsmith, I have seen enough AR barrels that were out of headspace to use as tent stakes. Never trust a manufacturer. The end user/installer should always verify unless you can guarantee the manufacturer NEVER makes a mistake.

 

[MagnumManiac]

You said the magic words "should be". In 50 years as a gunsmith, I have seen enough AR barrels that were out of headspace to use as tent stakes. Never trust a manufacturer. The end user/installer should always verify unless you can guarantee the manufacturer NEVER makes a mistake.

Are these AR barrels a pre-fit to a PARTICULAR rifle, or are they a GENERAL barrel for AR's.
This is TOTALLY DIFFERENT to a pre-fit for ONE ACTION…

I've been gunsmithing a long time, pre-fits don't exist here, but I can machine numerous barrels, chamber them and fit them to ONE ACTION, MY OWN.

You are all confusing what a pre-fit is.

Cheers.