Chambering steps for hobbyists

[urbanrifleman]

I do the same only never touch a cutting tool to a gage. Depth mic and indicators are the tools to use. Chamber deep, face off, set indicator to 0, depth mic, move to your number and finish face.

You chamber first then?

 

[VA_XTC_Shooter]

I've read on here and other places that turning the outside of a button cut barrel will open up the bore.
So if you chamber first, then turn the tenon, would you open up the chamber?

 

[Walt Krafft]

You chamber first then?

I do both. Lately I have been doing the chamber first. Not a lot of difference. I got bored one day and tried it. It doesnt change anything as far as touching off to set headspace. On a Remington, I set the GO gage 0 to .001 below the face. I turn the shank length to 0.001 to 0.002 less than the action and recoil lug measure.

 

[Will Henry]

You've read information which is not really credible with good quality barrels. All steels will move to a certain extent, but good quality button rifled barrels are stress relieved after rifling and are relatively inert. If really concerned about it, one could turn the tenon to near finished sized so that dimensions are little changed during threading. Honestly, I doubt that there is any measurable change anyway. I find it as easy to ream to depth as to face to length, and I lose no sleep over dimensional change which doesn't really happen to any significant extent. WH

 

[urbanrifleman]

I do both. Lately I have been doing the chamber first. Not a lot of difference. I got bored one day and tried it.

You complete me.

I use my kenna metal threading insert nearly exclusively now and my barrel threads have never looked better.

 

[jackieschmidt]

I've read on here and other places that turning the outside of a button cut barrel will open up the bore.
So if you chamber first, then turn the tenon, would you open up the chamber?

If you could measure the difference, you are a better Machinist than I am, and I am pretty darned good at it.

You will notice in the post I made about this subject is I rough turn everything within a few thousandths before I do the chamber. So any fears are negated.

 

[LVLAaron]

The little bit you take off for a tenon thread isn't gonna make a lick of difference.

Now, my (cheap) AR barrels with a 1/2 inch thread... you can put a pin gauge in the muzzle end and it will stop right at the shoulder.

 

[VA_XTC_Shooter]

The little bit you take off for a tenon thread isn't gonna make a lick of difference.

Now, my (cheap) AR barrels with a 1/2 inch thread... you can put a pin gauge in the muzzle end and it will stop right at the shoulder.

Is that because they are cheap and perhaps cut down prior to stress relieving?
I am just trying to better understand the potential changes to bore diameter when turning.

 

[LVLAaron]

I think so, yes. I've never noticed this on a Bartlein,Brux,Krieger barrel. But I've never cut them down that much.... But they're stressed relieved and cut rifled. A button rifled (lower cost) barrel will have stress imparted with the buttoning process.

 

[VA_XTC_Shooter]

I think so, yes. I've never noticed this on a Bartlein,Brux,Krieger barrel. But I've never cut them down that much.... But they're stressed relieved and cut rifled. A button rifled (lower cost) barrel will have stress imparted with the buttoning process.

Right that is my point. If turning a muzzle on a button barrel can open the bore, why couldnt turning around a cut chamber open the chamber? It sounds like there is a thickness parameter that would determine if the inner diameter opens or not.

 

[LVLAaron]

Two things..

1. How much are you turning off? On my mentioned AR barrels, there isn't much steel left between the bore and the threads.
2. How was the steel handled before you cut it?


FWIW: I have no problem cutting a 3/4 muzzle thread on a quality barrel. If the steel moves, I can't detect it. Slugs, pins, etc. If it does move... I'm sure the soft bullet spinning 200k rpm expands to fit the larger bore.

 

[VA_XTC_Shooter]

I was just running numbers for S&Gs. Comparing turning down a muzzle for 1/2x28 on a 223 barrel vs a chamber for say a 308, barrel wall thickness is similar percentage wise, but for the 223 barrel we are talking around 0.138" thickness remaining vs 0.302" thickness. I guess for the steel somewhere around that 0.138" number is the limiting factor.

Now I am curious what the thickness requirement is to not affect the inner diameter. Sounds like you found 3/4 to be fine, perhaps 5/8 too?

OP, sorry for derailing the thread, the process just raised the question in my head.

 

[Jonnyofalltrades]

I was just running numbers for S&Gs. Comparing turning down a muzzle for 1/2x28 on a 223 barrel vs a chamber for say a 308, barrel wall thickness is similar percentage wise, but for the 223 barrel we are talking around 0.138" thickness remaining vs 0.302" thickness. I guess for the steel somewhere around that 0.138" number is the limiting factor.

Now I am curious what the thickness requirement is to not affect the inner diameter. Sounds like you found 3/4 to be fine, perhaps 5/8 too?

OP, sorry for derailing the thread, the process just raised the question in my head.

Don't forget that the ID is going to collapse a little as soon as you apply any torque to the threads. Certainly more movement than any stress-induced shifting(at least in the case of the tenon). This radial loading is what causes a 60 degree thread(or 55 degree) to lock up and not work loose.
Muzzle devices are not usually torqued up as much, but there is always some movement, and it's not hard to feel it while slugging.

 

[Will Henry]

There is WAY too much emphasis on the stress imparted by button rifling. Every reputable maker of buttoned barrels that I know, stress relieves the barrels after rifling and before contouring. In fact, heat treatment is often the bottleneck in the operation. In addition, if stress relief was not done, any stress would be removed along with the material removed in chambering. If you rough with a boring bar or even a drill bit, the stress is removed prior to reaming. Either way, it's a non-issue.
Perhaps unrelated, but I have contoured numerous cut-rifled barrels which moved significantly when turned. Some even required straightening. This has never happened with any quality buttoned barrel, because they are stress relieved. WH