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Author Topic: M-N 91/30 Counterbores  (Read 2228 times)

JarheadAZ

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    • Greg Langelius *
M-N 91/30 Counterbores
« on: March 03, 2016, 06:24:52 am »
So I have this/these 91/30's and they are all counterbored. They shoot about the way I'd expect a rifle to shoot with a compromised crown; which is probably exactly the case.

As I see it, the rifles were given a lick 'n a promise sometime shortly after the cessation of hostilities on the Eastern Front, which included a one-size-fits all counterbored muzzle. The general appearance is that they simply used an oversized drill bit and ran it up the muzzle 'a bit'. This procedure was intended to cut away the portion of the blunderbussed muzzle that results when a Russian conscript drops the rod guide cap for the muzzle into the snow, and continues marching and scraping the interior of the the barrel end portion with the cleaning rod until it begins to take on the appearance of a trumpet bell. Apply cosmo and set it away for a half century and a score or so.

I never did crank up the courage to view this area with any reliable means of perception, but my estimation is that the 'step' from true bore to counterbore constitutes an internal crown and that it's probably a corroded mess. I further surmise that doing anything to it would probably be better than not.

So I purchased a 3/8" drill bit, got out my hand drill, and am at the stage where I am looking at them and a Mosin with some mild interest. Tentatively, the next step is to chuck up the bit, insert into the counterbore, and give the bit a few turns up against the 'internal muzzle' face.

Honestly, I doubt that wisdom plays any part in this plan; so I pause now to explain this plan to the forum and see what commentary follows.

Greg
Not lookin' to be in a gunfight, but if you find yourself mixed up in one, it might be kinda nice to have a gun...

"Faint heart never filled a flush" - Brett Maverick

Good marksmanship is no accident - JarheadNY

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    steve2md

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    Re: M-N 91/30 Counterbores
    « Reply #1 on: March 03, 2016, 09:23:56 am »
    Just don't go very deep. Barely scratch off the old steel until you have a clean surface. it might actually make an improvement. The idea of a crown is a SHARP transition from rifling to free flight at the end of the barrel. any burr left from drilling will throw your shot and screw any accuracy you could have gained. I used one of the large ball shaped grinding bits for a dremel chucked in my drill press and just touched the end a little at a time until it was right. That was on my M44 and it shoots half dollar size groups at 100 now. Plenty fine for a hunting/truck rifle.
    I'd suggest a drill press over the hand drill. use a torpedo level to make sure your barrel is truly vertical (having established that your press is truly vertical). Honestly though, if you're looking to squeak a little more out of your 91/30, I'd have a competent smith re crown it. The expense is worth the result. I'm willing to bet several of the smiths on here like Jesse or Doc will chime in soon....
    Heat it till it's hot, then beat it with a hammer until it's the shape you want.    Blacksmith's advice that works for pretty much everything in life

    JarheadAZ

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      • Greg Langelius *
    Re: M-N 91/30 Counterbores
    « Reply #2 on: March 03, 2016, 10:56:06 am »
    Yep, our ideas coincide fairly closely. My thoughts are a lot more about dressing the surface lightly than about going for broke. The Dremel ball is a better approach, too.

    I got one for $114, and the other two for $179 each. Not expensive, but not like before, either.

    I did a fair amount of add-on mods, but took scrupulous care not to make any changes that preclude completely restoring the rifles to original condition.

    Mods include a genuinely low and rigid scout mount, Allen stock packs for an improved cheekweld, and Slip-On Limbsaver recoil pads. Minimum dollars spent and some significant improvement gained over the original's shootability. Thinking mostly along the lines of a Volksgewehr

    Honestly, I cringe at the idea of any serious gunsmith spendage on these things.

    One thought I also had was about drilling some vents into the top surface of the counterbore only, to maybe counteract some of the muzzle flip; but that also makes a permanent alteration to the basic rifle.

    While I do handload for the 91/30, and my Son-in-Law has harvested a mess of Upstate NY Deer with his, I have refrained from doing any really serious load development on the 91/30 until I can get this crown issue resolved.

    Greg
    « Last Edit: March 03, 2016, 11:29:29 am by JarheadAZ »
    Not lookin' to be in a gunfight, but if you find yourself mixed up in one, it might be kinda nice to have a gun...

    "Faint heart never filled a flush" - Brett Maverick

    Good marksmanship is no accident - JarheadNY

    steve2md

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    Re: M-N 91/30 Counterbores
    « Reply #3 on: March 03, 2016, 01:00:00 pm »
    There is a muzzle break available for those that uses the front sight and a set screw. I'm not sure where I saw it now, but it would be better than drilling...
    Heat it till it's hot, then beat it with a hammer until it's the shape you want.    Blacksmith's advice that works for pretty much everything in life

    JarheadAZ

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      • Greg Langelius *
    Re: M-N 91/30 Counterbores
    « Reply #4 on: March 04, 2016, 06:27:49 am »
    I have one. It's now a (very heavy and expensive) paper weight.

    Muzzle devices that incorporate set screws appear to have one thing in common. They eventually end up somewhere downrange.

    Greg
    « Last Edit: March 04, 2016, 06:30:48 am by JarheadAZ »
    Not lookin' to be in a gunfight, but if you find yourself mixed up in one, it might be kinda nice to have a gun...

    "Faint heart never filled a flush" - Brett Maverick

    Good marksmanship is no accident - JarheadNY

    rubinschmidt

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    Re: M-N 91/30 Counterbores
    « Reply #5 on: March 08, 2017, 08:35:17 am »
    I've had some improvement by using 0000 steel wool and my thumb on milsurp muzzles that are not severely degraded. Just push and twist for a while, using the feel on your thumb to tell you when there is no longer any change. If you feel the wool catching on anything you know you need to continue. This method gently removes small burrs and reduces tiny pits without altering the rifle or risking real damage. I have seen some accuracy improvement, but bear in mind you can't make a tack driver if you're starting with a sewer pipe

    I tried the tried the grinding ball method before but it is very difficult to keep things aligned, and frankly wished I had not done it when I finished.  The rifle was not ruined, but I can't say I did it any good at all.

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