Barrel Prefit Methodology

[nksmfamjp]

I see most smith's want the action to properly fit the action to the chamber.

I get how Savage and the various nut guns work.

I was looking at the prefits which look like the guess and check method where a barrel maker chambers a barrel for a Rem 700 and if yours doesn't fit, somehow the gunsmith has to recut the barrel a couple thousandths to fit it.

but, I wonder….Could a chamber be cut to min length or just below, thread the barrel down on a GO gage, then measure the gap between Action and shoulder. Then final assembly with shims so it closes on GO, but not on NO GO. Anybody doing this? Unsafe?

 

[tobnpr]

I've never seen a shim system for this.
It is possible to headspace a new barrel by using an oversize recoil lug, and having it surface ground to the dimension needed to headspace- but you need a surface grinder or take it to a shop with one for best results. I've read where some will stone them, but that's not particularly precise.

You can request (depending on the barrel manuf) either short-chambered, or short-shouldered barrels. Most do one, or the other (or neither).

Most common is short chambered, as it does not require a lathe/machining. Deepen the chamber with a reamer/T-handle until the bolt closes on the go gauge. Tricky process, best to fit a reamer stop to the reamer- it's obviously easy to go too far which would then require machining the breech and shoulder. Depending on the chambering, they make "pull-through" reamers, which are run in through the muzzle.

If you have a lathe, but not the tooling for chambering (or just don't want to mess with it), the short-shouldered barrels are usually set up with the shoulder "short" by 20 or 30 thou, and are fully chambered. Barrel is dialed in on the lathe and the shoulder set back until headspace is correct.

Just some options...

 

[Boe]

The issue with a short chamber option is you don't have the reamer they short chambered the barrel with. The one you use will most likely have different dimensions. Could be leade, throat, neck, body, who knows unless you have the reamer print for both. Then you have to confirm the reamer manufacturer hit his numbers. That doesn't always happen. Otherwise you're going to have a ridge in the chamber somewhere. I've bore scoped a few of those chambers. I would suggest the short shoulder option. Get the chamber cut to full depth and set the headspace with the tenon
lenghth.

Richard Hilts
Hilts Accuracy Custom Rifles
www.hiltscustomrifles.com

 

[shortgrass]

The 'troubles' I see with either short chamber or short shoulder, besides what has already been posted in this thread, is to end up having optimum distance between bolt and barrel. You don't want too much, but you don't want to little.

 

[nksmfamjp]

Many of these issues are why I asked if a shim between barrel and action has ever been used? Typically a shim is bad in a real bolted joint, but these are really low torque joints mostly to hold position instead of clamp load.