Author's note: I wrote this in response to a question asked at InGunOwners.com. The responses were such that I thought maybe someone could benefit from it as an article instead of just an answer, so I'm sharing it out as such.
I've been getting asked on the board and via PM how I accurized my MN 91/30.
With all due respect to N_K_1984 and his hard work, I do not believe that the answer lies in floating the barrel. I'll get to that in a minute.
First, torque the action screws to 50in-lbs and shoot the rifle. It may be good the way it is! The PU snipers were just ones pulled from the line because they demonstrated better-than-normal accuracy.
If you're unhappy with the accuracy, you'll need to shim the sear spring/trigger/return spring. They're the same thing. Pull that piece out. While it's out, dress the sear down with a fine stone -- I like to work up to 600 grit for this, but any fine stone should work. Just don't change the angles! Also, stone the area on the sear spring contacted by the trigger. It's all very easy and straightforward.
Next, get a piece of shim stock. It should be 0.020" thick or so. Cut it to fit, drill a hole, and install it between the sear spring and the action. Do not go overboard; you should have an 8lb pull that resembles a revolver trigger. Any less, I consider dangerous, and if it's smooth, it doesn't feel like 8lbs.
Go shoot it. The improved trigger will help you get the inherent accuracy from your rifle.
Now, with regard to the barrel, there are two schools of thought: Floating and bedding. I am usually in the school that says float, but the barrel of the Mosin-Nagant is really too thin to float well.
With apologies to N_K_1984, I will pick on his targets because he has the most awesome sporterized Mosin-Nagant Ive ever seen. However, it needs improvement and this may help him some, too!
I believe this to be the first target he shot. The reason is that the three-shot group near the bullseye speaks of a cold barrel. However, as the barrel heated up, it threw the last two a bit high.
In what is probably the second target, you can see how the circle becomes pronounced.
I am guessing this is the third target shot. It shows a heated thin barrel: Its shooting large rings.
Floating a barrel is great, but only if its not skinny. A fix for this barrel would be a de-resonator about an inch in front of the stock, and a series of o-rings rolled down the barrel to the end, all touching. As is, the circles are not a whole lot bigger because the cosmetic thing he has hanging off the barrels muzzle is acting a bit like an old BOSS unit (its really doing something there, man, not just decoration as you stated in another thread!)
The next option is to bed the barrel.
1. Go to Autozone. Get thin cork gasket material. It should run you about $5.
2. Sand the barrel channel smooth, cut a strip of cork gasket material, and lay it in the barrel channel.
3. Put the barreled action back in, and cut off the excess cork wherever you see any.
Go shoot it. The bedding is allowing the stock and handguard to act as sort of a heavy target barrel. Thats not exactly right, but you wont be shooting circles and the harmonics will be way down.
Now, bed the action. Just pillar bed (instructions of all sorts are on the Web), heck, I just cut more cork and put it between the points on the action where the screws enter and the stock, then torque to 50in-lb. You just need known pressure points, not random ones.
The rest really depends on the ammo. The 7.62x54r uses .311 bullets, while domestic ammo uses .308 bullets. If you want accuracy, youre going to have to go with Priv Partisan or S&B. You can reload these cases too, and .311 bullets are readily available as are dies and reloading data. If someone will measure a 7.62x54r from Winchester, please post it. I may be wrong in that its still .308, but it was about five years back.
I hope this helps someone.
Copyright© Joshua M. Smith. I don't give a tinker's damn if you share this out or not; the "©" thing just seems to be in vogue right now! Haha!