Wondering if anyone knows at what points in the bore does the rifling twist rate change. Does it go from the 1 in 19 or so to 1 in 8 or so in one spot immediately or gradually get faster? Approximately how much of the muzzle 1 in 8?
Ultimately my goal is to counter bore the muzzle by about an inch or so and want to make sure I don't take off much if not all of the tightest twist section.
It is a gradual change, which makes sense if you consider how it would have been manufactured. Using a lathe or a rifling machine it would have gearing set up to progressively cut it. Very difficult if not impossible to cut it all one twist rate then switch instantly to another at some point in the barrel.
Rifling is basically just threading just in a very shallow narrow thread. Usually since you have multiple rifling (i.e. 2-6 normally being the common range with 4 being the average) it is basically the same thing as a multi-start thread.
The Italians actually had a issue with their M91 rifles when they converted many of them to the M91/24 pattern, which basically involved making them more like the T.S. short rifles they had. Since they shortened the barrels by a good amount it resulted in them cutting off most the slower twist and it resulted in horrible accuracy for those rifles. They stopped doing that after a few years and went back to making T.S. barrels from scratch for new production rifles as the cost savings wasn't worth the accuracy issues.
That being said if the end of the muzzle is garbage, counterboring won't hurt it more than it already is. I would however make sure it is the muzzle being worn out that is your problem. Many people have a tough time making these rifles shoot effectively due to the lack of proper sized bullets (.268 flat based bullets not .264 bullets, especially of the boat tail variety).
I second the accuracy issue with modern ammunition. I've only shot a couple of my carcanos and the bores are excellent in both but they can't hit the side of a barn door.
The muzzle is definitely am issue I can see, it for an inch or so it looks like a smooth bore, but I do reload for my moschetto and am prepared to make up some rounds with a handful of .264 projectiles as well as some correct .268s, since I've heard some shoot good with .264s. How much of the rifling would one say I would
---------- Post added at 12:50 PM ---------- Previous post was at 12:49 PM ----------
Be able to chop per say, without removing g too much of the fast twist?
You'll have to take out what's shaggy or you're not doing anything. You're only going to be removing an inch or so...I would think? Just clean it up. You don't have a choice, but how does it shoot as is?Originally Posted by 3rdTennCoC
Regards, Jim
I ordered it on line and did the paperwork yesterday so I have yet to take position of it, I intend to see how it shoots as is but I am brainstorming some possible solutions to the muzzle issue if it presents an issue
Basically if the muzzle is trash counterboring until the damage is gone is the only option other than rebarreling to bring some accuracy out of the barrel.
A M91 infantry rifle has a barrel length of approximately 30.71" (78cm). The twist difference is 11 per revolution over that length so if your removing 1" from the end by counterboring your twist should be approximately 1:8.35 at the end. Not a significant change and certainly one I wouldn't get too worried about. They mainly had issues with the M91/24s because they cut off about 12.9" which resulted in the twist going from about 1:8 to 1:12.62.
So you say I should be ok with twist rate takin an inch inch and a half off?
I would figure it should be fine, or at least better than what it is if the muzzle is destroyed.
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