Machining heavy barrel to a mid contour barrel?
- Thread starter Ghunter
- Start date
fingers284
CGN Ultra frequent flyer
- Location
- Alberta Cowboy Ranges
Any 'cold rolled" steel will react that way. Machine one side off of a CR flat bar and it will ALWAYS distort. Cold rolled Weldments will "pull" significantly more than mill steel of the same grade. I avoid CR for anything that needs machining but use it lots for "bolt-on's" where drilling is the only operation that is required.
I suspect that is because the cold finishing causes stresses in the steel, and these residual stresses result in the warping when stock is removed. If the steel were stress relieved after cold rolling, it would probably be stable when machined.
Years ago, I machined a significant number of 36" tapered octagon/tapered round muzzle loading barrels, starting with 1 3/16" diameter 1137 steel blanks. These were 24ga smoothbore, finished reamed.
Two warped on the lathe, one noticeably, the other dramatically. The first was salvaged as a carbine barrel, the latter as a long pistol barrel. None of the others exhibited warping.
I know one Canadian barrel maker elected to do his own stress relieving in-house, so he could have greater control. The steel ordered may very well be stress relieved by the mill. If blanks or barrels-in-process have to be sent out to a heat treater, the maker is dependent on an outside contractor.
rifleman762
CGN Ultra frequent flyer
- Location
- Southern Alberta
'Tis good enough for my purposes
. I'm not a 100 yard benchrest man. So improving my wind-reading ability is much more important for hit percentage than getting my group size lower than 1/3 MOA.I'd wager a guess it's the same for the OP. If he needed the tiniest group size, he'd likely be using something other than a 10/22.
I'll give you that for the absolute tiniest group size that you need to win a BR competition, a cut-rifled, 100% stress-free, 100% concentric barrel is the way to go. For the rest of us, it's a case of "that'll do". Diminishing returns and all that.
'Tis good enough for my purposes
I'd wager a guess it's the same for the OP. If he needed the tiniest group size, he'd likely be using something other than a 10/22.
I'll give you that for the absolute tiniest group size that you need to win a BR competition, a cut-rifled, 100% stress-free, 100% concentric barrel is the way to go. For the rest of us, it's a case of "that'll do". Diminishing returns and all that.
Thank you.
So, savage straightens barrels on a hydraulic press. So what? Would it be better if they used a lead hammer? straightening of the barrel is acceptable practice. Some makers will straighten a blank between the drilling and reaming process if the drill has wandered. Shilen does this. Shilen barrels are button rifled and stress relieved after rifling so any stress induced by the straightening process is eliminated. Shilen's barrels are competitive for any discipline.
Cold rolled steel is loaded with stress and, if it is to be machine to a specific shape and size, stress relief is necessary and it works well. As I mentioned before, even material which is sold as heat treated and stress relieved (HTSR) isn't always stress free and may need to be treated again if extensive machining is done. I experienced this with some HTSR 4140 which I was using to produce steering racks (for rack and pinion steering). When the first one warped when the teeth were cut, I set up a furnace and normalized the rest of the material and the problem was solved.
In truth, the only people who can really comment on the advisability of re-contouring rifle barrels are those who have done it enough to have seen the effect. The contention that only cut rifled barrels can be turned down or only cut rifled barrels are stress free is, indeed, a myth. By the way, even I, who have turned down hundreds of barrels, cannot say, absolutely, that a particular barrel will not warp. I can only say, in my experience, it will not warp. A particular barrel may have escape the stress relieving operation or it may be a cut rifled barrel which was made from material which was not stress free but was never stress relieved because it was believed that cut barrels don't need it.
In general, I don't hesitate to re-contour barrels. Virtually all of my hunting and match rifles have barrels which were re-contoured.
