Re-bore B weight swamped 50-cal to 54-cal?

[Flint62Smoothie]

Yes, I should probably call Bobby Hoyt, but does anyone know if a Colrain B-weight swamped 50-cal can be re-bored to 54?

 

[ApprenticeBuilder]

I seriously doubt that there is enough material in a "B wt" barrel to open it up to a .54

 

[Vaino]

I've used Rice's "B" weight bbl X 46" lg on many builds and Rice's maximum cal. for this bbl is .50 and I agree because the "waist" of the swamp is quite small......in fact, the bbl lug that's installed on the waist is soldered on in lieu of a dovetail. A shallow {.035} dovetail probably would be OK, but I still solder.

If you want a .54, why not buy a "C" weight bbl....not much increase in weight and it's readily available?....Fred

 

[Col. Batguano]

It's generally agreed that the narrowest safe wall thickness should be about .100". One can argue that cutting in a lug, and then re-installing the lug back in to the dovetail adds back in at least some of the reinforcement to the area, (making it less prone to fail) but in any event, it probably won't be as strong as it would have been had the dovetail not been cut in the first place.

Rice has several barrels they call a B-weight, with the following thicknesses at the narrowest part of the waist; .668, .710, .730, .732, .750. Allowing for the depth of rifling of around .012" that gives you the current wall thicknesses (using .012" deep rifling as a base line) in a .50 caliber of; .072, .093, .103. .113.

So it would seem that even if you soldered on the lug, there just isn't enough metal there for a total bore diameter (to the depth of the rifling) of .564".

That would only leave you wall thicknesses of the following; .052, .073, .083, .084, .093. Maybe it would be ok, and maybe it wouldn't, but with 12L 14 steel it's not the strongest alloy out there to try it with. In any case, the barrel itself is likely to be pretty whippy, and not very prone to good intrinsic accuracy.

 

[jerrywh]

The only way I would go that thin is if I used modern barrel steel. Even then you will have problems with other things, Like bolster thread depth etc.

 

[Flint62Smoothie]

Appreciate the input gents, thanks - was just curious.

 

[jbwilliams3]

I asked Charles Burton a few years ago if he could tell me what a B-weight .54 would weigh just because I was curious and he just said he won’t do higher than a .50 in B-weight. I imagine most, if not all, makers would be in the same boat.

 

[Col. Batguano]

If you're after a super light barrel done in a modern steel, why don't you contact the modern barrel companies like Likja, Criteron etc to see what they might be able to do. As far as weight goes, just do the calculation for the weight of the volume of steel for the tube for the bore for both a 50 cal, and a 54 in what ever length you want. A rough guess on the differential will be around .3 lb difference for a 44" barrel.

 

[Flint62Smoothie]

It was only a curiosity question guys ... my stock is rough inlet to the 'B weight' already and I'll live with that caliber, I was just curious - that's all. This will be for a custom build in left-hand.

I bought a used LH Lyman Great Plains to use in the meantime, which is in 54-cal ... hence the question.

But thanks all for the replies!

 

[don hepler]

I have a B weight Colerain swamped barrel, on a Tip Curtis rifle and one of the lugs, near the center of the barrel, is very close to the bore. I'm calculating about .100. That's a little scary, considering that my hand is pretty close to that area when shooting off hand.

 

[Col. Batguano]

Not sure about BP pressures, but a 30-`06 cartridge starts out around 50,000 psi at the breech, and 22" down barrel (in M1 Garand ammo) the pressure drops to less than 5000 psi in order to operate the op rod. Extrapolating that to our ML'ers, if we start at 10,000 psi at the breech, we should be about 10% of that at a similar distance down barrel. Remember too that the re-inserted lug is adding reinforcement, and, the tab portion is acting as something of an I-beam right there in the center where it's thinnest. Given the barrel is only thin at the tangent of bottom of the lands, unless you go really nuts with your loads you should be fine.

Since vent liners taper to a thickness of about 0.000" at their thinnest, doesn't it stand to reason that you would get some deformity in the vent liner lips (even though they are stainless steel) before the barrel is likely to give way some 20" down from the breech where the pressures are much higher?

I defer to the metallurgists and engineers on this page for greater guidance in the matter however.