Shimming a Mosin Action

[flmason]

Seems shimming the actions of Mosins is a pretty standard exercise out there. If I were to do this, should I inlet the stock to receive the shims or not? Was thinking the shimming could put the barrel and the magazine slightly further apart if I don't do the inlet work, or am I off base there? Don't have the disassembled rifle in front of me here.

[keith44]

never shimmed a mosin, I have shimmed a couple Marlin rimfire rifles though.  With them it did not cause any feeding problems, and helped to float the barrel.


I would like to hear other peoples experience with shimming a Mosin too.

[1911crazy]

On all my finnish mosins only the receiver is shimmed in the securing holes under the receiver  they install little u-shaped shims with the securing holes in them.
I have found these shims at both ends on both securing holes.   The finn's shimmed  the receivers in the stocks till they shot 1'' moa's.

[keith44]

was this done so the barrel would be semi-floated? or to relieve stress on the actions??

[zacharoo]

What are you using for shims and how thick?
Zacharoo

[flmason]

What are you using for shims and how thick?
Zacharoo

Haven't selected anything yet. Was thinking shims on the bottom side would separate the magazine and chamber some.  Was debating if I should inlet the wood to make up the difference? I one shims the top, same problem I would think. But you might remove wood on the bottom side to keep the relationship of magazine to barrel but raise the action slightly, to free float some?

[Buckskin]

I have shimmed a couple of 91/30 M/N's and it really made them accurate. You can use metal but I used pieces of those plastic fake credit cards that you always get in the mail trying to get you to use their card.  I placed a piece with a hole drilled in it under the front ring where the action screw screws into the action and one under the back action screw. This raises the action up enough to allow the barrel to float. I have found brass pieces under these two spots on Finn rifles. Also I took a piece of wool felt cloth 1 inch wide and long enough to wrap it around the barrel for a length of about 4 inches. I put some oil on the felt piece and wrapped it around the barrel about 2 inches back of where the barrel exits the forearm and then placed the top hand guard on. This will cushion the barrel and allow it to move during the harmonic movement of the barrel during firing but not allow it to come up hard against the wood. It also helps keep the barrel lined up squarely. This is how the Finn's did it also.

All you need to do then is slug your bore to see which bullet size it needs. Either a .311 or .312 diameter. If you slug measures .310 to .3105 between high spots left by the grooves use a .311 diameter bullet if it measures .3105 to .3115 use a .312 diameter bullet. If it measure larger than .3115 and you don't want to shoot cast bullets then get rid of it and get you another one. It will not shoot accurately with jacketed bullets.

Once you find your bullet diameter needed then get you some Accurate 4350 powder, and CCI 200 primers and load up using either .311 174 gr Sierra Match Kings or 180 gr SP COAL 3.000 or for .312 bullets use the Hornady 174 RNSP COAL 2.790 and use a Lee Factory Crimp Die on all loads. This is the most accurate load that I have found for all M/N's.

Good luck and good shooting.

This what 1shot recommended from the MilSurpus forum.  I shimmed and wrapped the barrel exactly as he recommended and mine shoot's unbelievable. I shot at 50yds with about 1" groups. With  bayonette on 4" high and dead center, with it off 7" high and 3 inches right.  Both groups were just over an inch and had similar results at 100 yards, probably closer to 1 1/2" groups with the bayonette on 8" high, with the bayonette off - didn't hit the target... Clearly this gun shoots better with the bayonette, which is fine I kind of like the balance when shooting off hand with it on.
 

Just for fun and because I was shooting so high, I ran the target out to 300yds.  This is what blew me away, I shot 8 shots and every single shot was well inside a paper plate and the 4 center shots would have hit a grapefruit!  Still 4" high, but pretty dog gone good group with a baseball bat for a front sight.  I have bolt guns with variable scopes that fight me at that range.

[flmason]

I have shimmed a couple of 91/30 M/N's and it really made them accurate. You can use metal but I used pieces of those plastic fake credit cards that you always get in the mail trying to get you to use their card.  I placed a piece with a hole drilled in it under the front ring where the action screw screws into the action and one under the back action screw. This raises the action up enough to allow the barrel to float. I have found brass pieces under these two spots on Finn rifles. Also I took a piece of wool felt cloth 1 inch wide and long enough to wrap it around the barrel for a length of about 4 inches. I put some oil on the felt piece and wrapped it around the barrel about 2 inches back of where the barrel exits the forearm and then placed the top hand guard on. This will cushion the barrel and allow it to move during the harmonic movement of the barrel during firing but not allow it to come up hard against the wood. It also helps keep the barrel lined up squarely. This is how the Finn's did it also.

All you need to do then is slug your bore to see which bullet size it needs. Either a .311 or .312 diameter. If you slug measures .310 to .3105 between high spots left by the grooves use a .311 diameter bullet if it measures .3105 to .3115 use a .312 diameter bullet. If it measure larger than .3115 and you don't want to shoot cast bullets then get rid of it and get you another one. It will not shoot accurately with jacketed bullets.

Once you find your bullet diameter needed then get you some Accurate 4350 powder, and CCI 200 primers and load up using either .311 174 gr Sierra Match Kings or 180 gr SP COAL 3.000 or for .312 bullets use the Hornady 174 RNSP COAL 2.790 and use a Lee Factory Crimp Die on all loads. This is the most accurate load that I have found for all M/N's.

Good luck and good shooting.

This what 1shot recommended from the MilSurpus forum.  I shimmed and wrapped the barrel exactly as he recommended and mine shoot's unbelievable. I shot at 50yds with about 1" groups. With  bayonette on 4" high and dead center, with it off 7" high and 3 inches right.  Both groups were just over an inch and had similar results at 100 yards, probably closer to 1 1/2" groups with the bayonette on 8" high, with the bayonette off - didn't hit the target... Clearly this gun shoots better with the bayonette, which is fine I kind of like the balance when shooting off hand with it on.
 

Just for fun and because I was shooting so high, I ran the target out to 300yds.  This is what blew me away, I shot 8 shots and every single shot was well inside a paper plate and the 4 center shots would have hit a grapefruit!  Still 4" high, but pretty dog gone good group with a baseball bat for a front sight.  I have bolt guns with variable scopes that fight me at that range.

Thanks much.

Interesting that the idea is soft cushioning. Have to admit, not familiar with 4350. Will have to look that up.

Have used primarily 4198 in the past as I had a .223 and .30-06 and seemed a fair choice for both, IIRC. Its been at least 17 years since then. One was Mini-14 other was a refurb'ed Garand. Never got truly great accuracy out of either though. Not enough time invested and was always picking loads I thought would cycle the actions reliably. Not an issue with M/N. Miss both of those guns though, for sure.

[Buckskin]

I have shimmed a couple of 91/30 M/N's and it really made them accurate. You can use metal but I used pieces of those plastic fake credit cards that you always get in the mail trying to get you to use their card.  I placed a piece with a hole drilled in it under the front ring where the action screw screws into the action and one under the back action screw. This raises the action up enough to allow the barrel to float. I have found brass pieces under these two spots on Finn rifles. Also I took a piece of wool felt cloth 1 inch wide and long enough to wrap it around the barrel for a length of about 4 inches. I put some oil on the felt piece and wrapped it around the barrel about 2 inches back of where the barrel exits the forearm and then placed the top hand guard on. This will cushion the barrel and allow it to move during the harmonic movement of the barrel during firing but not allow it to come up hard against the wood. It also helps keep the barrel lined up squarely. This is how the Finn's did it also.

All you need to do then is slug your bore to see which bullet size it needs. Either a .311 or .312 diameter. If you slug measures .310 to .3105 between high spots left by the grooves use a .311 diameter bullet if it measures .3105 to .3115 use a .312 diameter bullet. If it measure larger than .3115 and you don't want to shoot cast bullets then get rid of it and get you another one. It will not shoot accurately with jacketed bullets.

Once you find your bullet diameter needed then get you some Accurate 4350 powder, and CCI 200 primers and load up using either .311 174 gr Sierra Match Kings or 180 gr SP COAL 3.000 or for .312 bullets use the Hornady 174 RNSP COAL 2.790 and use a Lee Factory Crimp Die on all loads. This is the most accurate load that I have found for all M/N's.

Good luck and good shooting.

This what 1shot recommended from the MilSurpus forum.  I shimmed and wrapped the barrel exactly as he recommended and mine shoot's unbelievable. I shot at 50yds with about 1" groups. With  bayonette on 4" high and dead center, with it off 7" high and 3 inches right.  Both groups were just over an inch and had similar results at 100 yards, probably closer to 1 1/2" groups with the bayonette on 8" high, with the bayonette off - didn't hit the target... Clearly this gun shoots better with the bayonette, which is fine I kind of like the balance when shooting off hand with it on.
 

Just for fun and because I was shooting so high, I ran the target out to 300yds.  This is what blew me away, I shot 8 shots and every single shot was well inside a paper plate and the 4 center shots would have hit a grapefruit!  Still 4" high, but pretty dog gone good group with a baseball bat for a front sight.  I have bolt guns with variable scopes that fight me at that range.

I should mention that the above groups were shot with PRVI 182 grain store bought... I bought 100 rounds of this prior to slugging my barrel so I could have some brass for reloading. Mine slugged nearly .313, but still shot the factory stuff great.  I do have some Hornady 174's loaded up and ready to go if the wind ever dies down, but also have 4 other calibers that need shooting as well.  Also, I want to try and find some other .312 bullets with higher bc, round noses aren't my first pick of bullet style.