View Full Version : Tight fit with Silver Bear in a Mosin
July 17, 2009, 04:22 AM
I bought some silver bear SP's for hunting purposes. But when I chamber a round it seems like it takes a little more effort to lock the bolt. The rifle I have is a M91/59, a refurbished M91/30 cut to carbine length with the 1100-2000 markings ground out of the rear leaf. The rifle looked to be in fairly unfired condition when I first got it and has a good bore.
Since the bolt locks (I haven't fired yet) would it be safe to fire or am I risking having it blow up in my face? (Slim chance but I want to be sure first)
July 17, 2009, 11:09 AM
Have you fired this rifle, and if so, with what ammo?
Thoughts, in order of likelihood:
1) Dirty chamber, most likely coated with cosmo. Clean it thoroughly with mineral spirits and then lightly (lightly!) coat it with quality gun oil to prevent rust.
2) Dirt under the extractor. The Mosin-Nagant extractor rotates with the bolt head, but the cartridge tends to stay stationary in the chamber, so the extractor drags along the case rim and creates friction. Compared to the common copper-washed steel-case milsurp ammo, a dirty extractor will be more obvious with Silver Bear because the dirt will tend to stick to the lacquer-coated case.
3) Inadequate clearance between the extractor and the bolt head. Remove the bolt head, clamp it in a vise, and give the extractor a few light taps forward with a punch.
4) Burr or rough edges on the extractor. Remove it, lightly stone the underside, and put a slight chamfer on the edges.
5) Burr or rust in the chamber.
July 18, 2009, 02:25 AM
Yes I have shot this rifle with commercial ammo (Hot Shot I think is the brand, 180 gr) and I don't notice a tight fit with any other ammo besides the Silver Bear. I picked up some Brown Bear but have yet to try a fit. There isn't a difference in chamber size between newer 7.62x54r rifles and the old Mosins, is there?
July 18, 2009, 02:43 AM
Mosin-Nagant riles, especially those made during the war(s) and in satellite bloc countries, tend to have bores between .307 and .313 due to quality control issues. Specimens made in Finland are the best, followed by Russia proper. You can identify yours pretty easily by the markings, check it out at: http://www.7.62x54r.net (http://www.7.62x54.net)
I have two and one has a much tighter bore, thusly is more accurate and hotter to the touch after repeated firing.
July 18, 2009, 05:02 AM
Mine is a M91/59. An M91/30 that was refurbished and cut down to carbine length. I believe it has the Tula cartouche on the receiver top but the stock is different as it was assembled somewhere else. I think Bulgaria. I did the research once but I didn't write anything down so I'm at a loss. :o
I have a friend who can help me with barrel bore sizing and headspace/chamber issues. I might see him on Sunday.
Again, the problem is more that it's a tight fit. It more feels like the bolt is a few thousandths off when I lock the bolt down so it might be issues with QC in the ammo (cheap stuff).
July 18, 2009, 05:25 AM
Best of luck... fun rifles they are, gems of engineering they are not!
July 18, 2009, 05:59 AM
Here is an example of the 91/59
July 19, 2009, 05:27 AM
Ok, I got out a few different rounds to try in the chamber.
Winchester White Box SP:
Fit fine, was a little stiff on the lock but seemed to move all the way forward with correct tolerances of gauge
Hot Shot SP:
Perfect fit, it was what I used for deer season and did a marvelous job on the animal too, quick clean ethical kill.
Hot Shot FMJ:
Same as the Winchester SP, a little stiffer.
Brown Bear SP:
Again about the same as the Winchester and Hot Shot FMJ's.
Silver Bear FMJ:
Tighter than the winchester but not alarming, needed just a little more pressure to lock.
Silver Bear SP:
These were noticeably more difficult to lock into battery, almost as if the bolt didn't travel forward enough but was still enough that a little extra force gets the bolt locked.
ETA: Here she is with the M1903
July 25, 2009, 09:13 PM
The Silver Bear casings are Zinc plated on steel - the Zinc plating tends to be a bit thicker and less uniform than other coatings - e.g. lacquer or copper wash. I've had the same experience with Silver Bear ammo in other calibers and other combloc weapons. Nothing wrong with your rifle (more than likely) the problem lies with the ammo - so long as it shoots and extracts - the tight fit is not a real problem.
July 28, 2009, 11:40 AM
the same thing happens to my mosin when i use copper washed czech ammo, it doesnt chamber or extract well at all. Ive had my chamber polished also so i know its not a burr or cosmo. some mosins are just funny like that
July 28, 2009, 12:38 PM
This past weekend I went out to the gravel pit to shoot off some steel cased surplus ammo and every magazine had a really hard to clear stoppage (wish I had taken a picture 'cuz it's hard to describe). The round feeding from the magazine would stovepipe sort of and get stuck on a little tab which I think keeps the round in the mag. This tab is about 3/8" long and sticks out <1/4" on the left side of the chamber if you are looking from the top with the stock in your lap and the barrel facing downrange. I think the root of the problem is that it was freaking hot and the waxy coating was melting and causing the cartridges to hang up while feeding. I had to use my pocket knife to depress the tab while pulling with the fingers of my other hand, which inadvertently got cut by the sharp edges inside the chamber and magazine... leading to a rather uncomfortable day at the range. At least there were no Polish separatists shooting back at me (that's why I love mil-surp shooting!)
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