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Posted: 7/5/2013 2:16:55 PM EDT
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Guys
I have a well worn m91/24 Carcano carbine. The bore is frosty, but has quite strong rifling. Anyway, I took it out to the range the other weekend, and had a couple of problems. First off, although it chambered and locked the rounds in with no problem, it took a good couple of hard whacks the palm of my hand to unlock the bolt. The brass does not show any signs of high pressure (stretch marks, flattened primers), but does have a little spot on the OD of the extractor rim that looks like it is a little flattened. I was shooting both old Norma, and new Prvi 139 FMJ ammo. The Norma seemed to be more difficult to unlock then the Prvi, although both had the slightly flattened rims. The locking lugs on the bolt, and what I can see of the receiver look good. The bolt is un-numbered. It also shot like crap! My M41 rifle was using the same rounds, and was grouping nicely. I have slugged the bore on the carbine, and it is .268 in the grooves, so I think the bullets on the two loads may be a bit undersized for it. Once I get the lock up problem figured out, I will try some .268 Hornady SP bullets, those are pretty straight walled, and will have lots of bearing surface. I am certainly more concerned about the bolt lock up issue! Although I don't have headspace gauges, 3M masking tape measures out pretty consistently at .005, an observing the scuffing on the base of the taped case gets you in the ball park! For those who are worried, I fired 10 rounds off of a shooting vice with a string hooked to the trigger before I put it up to my face!  Then, I checked over each piece of brass and the rifle after each shot.
Like I mentioned above, tight lock up after firing is usually an overpressure issue (from what I have read). Anyone have a suggestion? Thanks! |
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Hi,
I wish I could help but, I have had the same problem with my 91/24 also. It is intermittent but, the head space is correct and without issue as far as I can tell. I haven't been able to make heads or tails of why this happens every once in while? As far as the keyhole and poor accuracy, I understand with the carbine everything comes down to the bullet. I have been running mostly the Graf and Sons (Hornady) at the .268 which I understand is the best bullet for the gun. Even with this, the accuracy has only been marginally better than when I ran some privi through it. |
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I'm gonna blame the "frosty" bore.
A rough bore can lead to high chamber pressures. It simply takes a lot of power to push a bullet through a high-friction bore, and pressures can skyrocket. That would also go a long way toward explaining your accuracy troubles. I'd lap the bore smooth, as long as I didn't care about any negative influence that might have with any collector value. (No idea with a Carcano.) |
| I had the same issue with my 91/28 moschetto ts. I talked to a friend in TX who's a carcano collector and he told me there are two bullet diameters in production for the carcano, .264 and .268. I had my tight lock up with hornady .268 so he suggested I get some .264 and try it again. I haven't bought any 264 yet but I think the issue will go away with the smaller bullets. He gave me a long answer that boiled down to some bores saw alot of action and have loosened up and some were shot very little plus some slight variances between manufacturers and suppliers. Mine is a Beretta Gardone made in 1936. I would try this as its a starting point, if not I have no idea where to look. |
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Hard extraction w/o signs of overpressure is often caused by a "Sticky" chamber... caused by something like baked in cosmoline or a buildup of residue from laquered steel cases. This is fairly frequently encountered with Mosin Nagants. Make sure everything is super clean.
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Thanks for all the replies.
The carbine had been packed with grease, so much so that I had to punch the bore at the LGS to make sure it even had rifling. Anyway, the bore/chamber is clean because I spent almost an hour getting the grease out! The bore actually cleaned up better after shooting, I guess the FMJ loosened some of the built up stuff up. Anyway, it is in nice shape, just lightly frosted. I thing my tight lock up problem may be something in the bolt. I made up a dummy round, and tried chambering it a few times. It appears my bolt sometimes wants to stick when opening (cocking), I need to read up on how to get it apart, and see if something is broken/burred/caked with gunk! |
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Quoted:
Thanks for all the replies. The carbine had been packed with grease, so much so that I had to punch the bore at the LGS to make sure it even had rifling. Anyway, the bore/chamber is clean because I spent almost an hour getting the grease out! The bore actually cleaned up better after shooting, I guess the FMJ loosened some of the built up stuff up. Anyway, it is in nice shape, just lightly frosted. I thing my tight lock up problem may be something in the bolt. I made up a dummy round, and tried chambering it a few times. It appears my bolt sometimes wants to stick when opening (cocking), I need to read up on how to get it apart, and see if something is broken/burred/caked with gunk! If you haven't taken apart the bolt and cleaned it inside then it is almost surely full of cosmoline or gunk... It should operate much smoother with a proper cleaning and fresh oil. |
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The 91/24s were converted from 91 long rifles. 91 long rifle utilized a "gain" twist rifling. This means there is almost no twist at the chamber and it gets tighter as you get to the muzzle.. When they converted them to 91/24s....they chopped the "fast" twist part of the barrel off. They didn't shoot well back then....and are some of the least accurate of the Carcanos. BTW the M/41 has standard rate rifling..it's the same from breech to muzzle...... |
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