Mosin Nagant heat issues

[kouye]

After shooting a group of 5 rounds through my 91/30 (about 30-45 seconds in between rounds), the next group of 5 seems to get a little larger, and the next group is all over the place. This is with a scoped rifle so I don't think I'm doing anything differently.

I've resorted to only shooting 2 groups of 5 before alternating guns. I was just curious if this is normal behavior or not. How many groups can you shoot before you start having issues?

[Powerkraut]

Shim the action, sand the barrel channel, and cork it. Play around with pressure points and this should cease to be an issue. It's a really common problem with most milsurp rifles that were cranked out in wartime, as the barrel heats up it expands and contacts different pressure points in the barrel channel effecting accuracy.

[MalC]

Strange, I can fire off rounds fast enough to make tiny drops of cosmoline that I missed sweat out of the stock, and my groups still don't go all over the place. The first few cold shots are a little more dead-on, but I don't see the big drop in accuracy you describe until the barrel is so hot it's uncomfortable to hold.

The 91/30 has a hilariously-thin barrel so this doesn't surprise me, but I have no clue why it's happening to yours so quickly. Did you use the same ammo the whole time? If you ran out of one batch of surplus and started shooting a second batch half-way through, that could account for your groups going to hell. My 91/30 loves some surplus ammo, but others give me minute-of-barn accuracy if I'm lucky.

Sorry I can't help more

Edit: I've also sanded down the inside of the forearm/handguard using a socket from a ratchet wrench covered in sandpaper, and cut up some of that thin cork sheeting to bed the barrel in there snugly. http://www.gunandgame.com/forums/mos...nt-pt-2-a.html <---here is an explanation I found with a google search.

[kouye]

Shim the action, sand the barrel channel, and cork it. Play around with pressure points and this should cease to be an issue. It's a really common problem with most milsurp rifles that were cranked out in wartime, as the barrel heats up it expands and contacts different pressure points in the barrel channel effecting accuracy.

I have been messing around with shims under the action and cork near the end of the barrel. Perhaps I don't have the cork in the right place.

I also put cork under the chamber just in front of the recoil lug based on the drawings of where the Finn's wanted to make sure there was even pressure.

I may have to take everything out and start over and take better notes of what happens with each change.

[kouye]

Strange, I can fire off rounds fast enough to make tiny drops of cosmoline that I missed sweat out of the stock, and my groups still don't go all over the place. The first few cold shots are a little more dead-on, but I don't see the big drop in accuracy you describe until the barrel is so hot it's uncomfortable to hold.

The 91/30 has a hilariously-thin barrel so this doesn't surprise me, but I have no clue why it's happening to yours so quickly. Did you use the same ammo the whole time? If you ran out of one batch of surplus and started shooting a second batch half-way through, that could account for your groups going to hell. My 91/30 loves some surplus ammo, but others give me minute-of-barn accuracy if I'm lucky.

Sorry I can't help more

I'm just about to end my 880 rounds of '72 Russian steel core light ball surplus, so I am using all of the same batch of ammo.

I'm going to try several different ammo when it arrives sometime next week, including 182 gr surplus as well as some of the more expensive non corrosive stuff.

[Powerkraut]

I have been messing around with shims under the action and cork near the end of the barrel. Perhaps I don't have the cork in the right place.

I also put cork under the chamber just in front of the recoil lug based on the drawings of where the Finn's wanted to make sure there was even pressure.

I may have to take everything out and start over and take better notes of what happens with each change.

Make sure you sand the barrel channel some, both of mine already had shims under the trigger guard so I just added two more in the standard position, corked under the chamber and the nose cap. Results haven't been great on one of them, but I think that is more due to the crown.

Start with under the chamber and the nose cap, then play around adding cork under the top hand guard at either end and pieces in the corresponding locations on the stock.

[6mmintl]

Heat mirage seen thru scope?

[kouye]

Make sure you sand the barrel channel some, both of mine already had shims under the trigger guard so I just added two more in the standard position, corked under the chamber and the nose cap. Results haven't been great on one of them, but I think that is more due to the crown.

Start with under the chamber and the nose cap, then play around adding cork under the top hand guard at either end and pieces in the corresponding locations on the stock.

Yeah, sanded with a 1/2" socket wrapped with sandpaper. Checked the gap under the barrel by sliding a piece of paper between the channel and barrel and it seems to be even from the cork at the nose to the chamber. How about the hand guard on top? I've tried with and w/o cork on top and I didn't see any different results in the heat issue or precision.

I think I'll leave the gap checking paper under the barrel and sticking out the sides when I go to the range tomorrow. Then I can check for the barrel touching after shooting 10 rounds w/o removing anything.

[kouye]

Heat mirage seen thru scope?

Hmmm...I don't think so, but how would I be able to check?

[bbm]

If it keeps giving you problems cut off 6 inches of the barrel and get another stock and make it a Sporter!!!!!

[Powerkraut]

Yeah, sanded with a 1/2" socket wrapped with sandpaper. Checked the gap under the barrel by sliding a piece of paper between the channel and barrel and it seems to be even from the cork at the nose to the chamber. How about the hand guard on top? I've tried with and w/o cork on top and I didn't see any different results in the heat issue or precision.

I think I'll leave the gap checking paper under the barrel and sticking out the sides when I go to the range tomorrow. Then I can check for the barrel touching after shooting 10 rounds w/o removing anything.

Make sure your pressure points are tight enough too, I hit the hanguard with a 14mm socket but make sure you don't sand the edge.

Just to be clear, groups tighten up again after letting it cool down in the same range session right?

[kouye]

Yes, after letting it cool off for say 20 minutes it tightens up again but goes off pretty quickly.

I'm going to redo the shims and cork and make sure I'm keeping the pressure points even. I have a feeling that they are uneven now and making things even worse.

[Powerkraut]

Shims should be fine if it tightens up after cooling down, make sure the cork is nice and tight at the nose cap, if that doesn't help try corking the whole channel. Make sure you soak the cork in oil so it won't be an accumulation point for moisture.......found that out the hard way.

[kouye]

Hmm...I hadn't thought to oil the cork....

Well, I did find that I had to add a tad more shim at the recoil lug and tang to float the barrel w/o the cork up front. Now, I think the pressure is a bit more even. Not sure if that'll help at all but I feel better about it.

I also found the front trigger guard bolt wasn't torqued down evenly with the tang bolt. Not sure what happened there, but it's likely that I just forgot to do it. I set them at 40in/lbs.

[MalC]

If it keeps giving you problems cut off 6 inches of the barrel and get another stock and make it a Sporter!!!!!

BLASPHEMY!!! If you can't stand still and poke stuff 20 ft away with the bayonet attached, it isn't a 91/30.