Barrel thickness?

I am wanting to put a 15/16" 1/70 twist Green Mountain .54 barrel on a RMC stock and am wondering if it would be safe. The design of the stock has a bolt instead of a wedge to hold the barrel to the stock. A .050 deep groove would be required to get the bolt thru. So here are my calculations...

15/16" minus.567(groove to groove)= .3705
.3705/2 = .18525
.185 minus .050 deep groove (where a key would go)-.13525 thick at the key. Would it be safe with 100 grains of powder?

I would shoot it. Pressure at the lug will be less than breech pressure.

In an M1 Garand breech pressure is about 50,000 psi, and 23" down barrel,

I wanted to do the same thing, and 0.2 was the standard minimum thickness. I was going to have mine rebored to 54, so I chickened out. So I am sending my Accusporter with set trigger down the road. Hope I don't miss it. Good luck.

I think 0.2 is more than you need for minimum thickness, particularly as you get down bore from the breech.

Rice makes a B-weight in 50 cal that is .732 at the thin spot mid waist. Allowing for depth of rifling of .12 (on each side, that only leaves .012 wall thickness at the depth of the rifling as the barrel leaves the factory. I imagine that if it were an unsafe barrel at those thicknesses, we would have heard about it by now, and their lawyers would have made them stop making them.

0.08 is often tossed around by the barrel builders as being the absolute minimum.

When I install staples or cut for sights, under lugs etc as long as I have 0.1 I personally feel more than safe with that.

If I can't keep 0.1 then I solder...

The re-inserted lugs in to the dovetail will add back in reinforcement too.

I would be curious if any of our engineers here on the forum have done the calculation of what pressure it would take (given the pressure curve of burning BP) to make 12L14 steel fail in a thin line like we get with the tangent of a lug dovetail, and with the sorts of thicknesses we're talking about.

Just a wild guess is that with our typical pressures, a thinning like that (at the first lug) might be ok all the way down to a thickness of .01 before it would fail. It's just a guess though. I think stainless steel is tougher, but the lips on our touch hole liners don't seem to distort outward, and breech pressures are much higher than pressures down barrel.

This help

12L14 free machining steel Minimum Properties
Ultimate Tensile Strength, psi 78,300
Yield Strength, psi 60,200
Elongation 10.0%
Rockwell Hardness B84





William Alexander

I wouldn't post any number here. But look up hoop stress. Ignore the octogon part and assume it's a cylinder the thickness of the thinnest spot.

A big one is stress risers. A rough nick or gouge will reduce the ultimate pressure it can withstand by a good mark.

However, I own a 15/16ths lyman GPR with a 54 cal bore. I put 90grs of FFFg goex in it.

You using roundball only, or using concials?

I believe folks have done .030 dovetails before. You could solder it in after you dovetail it.