I'm looking real hard at the .45-70 barrel dimensions. Obviously, I'd like to reduce weight on the .45-70 as much as possible.
I'm concerned about the barrel thickness underneath an RPK gas block, which is going to be approximately .166" assuming a .458 barrel. Would that be thick enough for the mid-section of the barrel? Seems a bit thin to me. That would be OK for the muzzle, I would assume, but for that area, the gas pressure is probably still hot enough to make that small a section a problem.
Like VZ58, I'll probably make my own gas block that is thicker at the base. I have a spare gas block set aside for the build, which I plan to weld to a chunk of DOM tubing for the "base" that will go around the barrel.
I'm stumped about one thing. The article about the Dragunov (actually a PSL) in .50-110 caliber looks like it is using a Yugo gas block. If so, then that's an even thinner barrel at that part. Doesn't sound right to me.