.312 bullet ok 310/311 grooves?

[Osage]

Accidentally got the wrong box of bullets for my mosin. I slugged the barrel and got either 310 or 311 on the grooves. Would 312 bullets be safe?

[Sport45]

I'd say so. Just start at minimum charge weight and work your way up as usual.

I've shot a lot of .310 123gr AK bullets in .308 when we used to get them for $30 a thousand or so.

[IllinoisCoyoteHunter]

Yup. Shoot 'em!

[T. O'Heir]

"...got either 310 or 311..." Hi. You'll get one or the other, but not both. However, Mosin barrels are rarely larger than .310". Lee-Enfields they ain't. Mind you, 2 thou won't make much difference.
"...shot a lot of .310 123gr AK bullets in .308..." Way undersize. They'll rattle down the barrel.

[243winxb]

Should be OK. Use a starting load.

[res45]

You should be safe as long as you use the starting load and work the load up slowly looking for any pressure signs. In general you want jacketed bullet to be no larger than you actual groove to groove bore dia. cast bullets on the other hand you will want to be from .001 to .002 over grooved dia.

Jacketed bullet have a harder copper or bi metal jacket with a Brinell hardness of 100 +. Jacketed bullet produce more bullet to bore friction this increases pressure,cast bullets on the other hand are much softer on the Brinell hardness scale they run anywhere for 5 BHN pure lead to the high 20's BHN. Lead or hard cast lead bullets produce less friction and pressure and can be squeezed down much easier.

Some military and commercial barreled rifle and larger cal. guns were equipped with a squeeze bore,this allow over caliber bullet to be fired in rifle and larger guns,pressure still increases but at a much more gradual rate. I believe at one time the Ruger Mini 30 was equipped with such a barrel they may still be.

As far as Mosin barrels being rarely larger than .310 groove to groove dia. I have not found this to be the case. It's more common in the Finnish Mosins where you find bore dia's in the .308" to .309.5" dia. range with an occasional .310 M39 bore .310 dia. bores in a Russian Mosin are rare most run in the range of .311 to .313

All my personal Mosin rifle as well as my brothers all slugged out at .312 groove to groove dia.they shoot the .311 dia. jacketed bullets and .314 dia. cast bullets the most accurately.

General specification of Mosin rifles.
http://7.62x54r.net/MosinID/MosinSpec.htm
http://7.62x54r.net/MosinID/MosinSlug.htm

[FrankenMauser]

A half-decent Mosin barrel should slug smaller than .313", but it is not uncommon to find examples that were poorly cared for, with bores as bad as .318".

"...shot a lot of .310 123gr AK bullets in .308..." Way undersize. They'll rattle down the barrel.

He was referring to shooting .310" projectiles in a .308" bore ... another example of 'putting the squeeze on'.


If you can get the bullets to chamber safely (not contacting the throat): Start low, and work up. That extra 0.001" (maybe 0.002") will increase pressure slightly, but should shoot just fine.

[Osage]

I made several loads this weekend starting at the min load recommended by hornady and lee. I have tried some speer 150 gr 311s but had lots of fliers. Thinking it could be the gun I took the barrel out last night and sanded down the channel and added a piece of aluminum tape under the end of the barrel to make sure she floats. I'm going to pick up some sinkers today and slug again to be sure. A 308 bullet goes into the bore almost to the cannelure. Gun is a1922 izzy with rearsenaled laminated stock. Great bore, should be a good shooter.

[FrankenMauser]

Be sure to get pure lead, or soft lead alloy sinkers, if that's what you plan to use. The Zinc crap that's showing up more often won't work well (and often contains steel shavings).

[Osage]

Finally made it back out with some new loads. Knowing that Prvi factory ammo shot well, I decided to try much lighter loads. Groups were much better. Pretty good in fact. 174 gr hp bt with 42.5 gr varget was about the best although the holes were still in a slight vertical string. All loads did that though. Gun was no longer shooting low but slightly high were it's suppose to be. I guess it just likes plinking loads.

[mkl]

Here's an interesting test by P. O. Ackley regarding oversize bullets.

He fed an 8mm (.323) down a 30 caliber (.308) pressure barrel.

No pressure increase!

But note the chamber was cut so the 8mm bullet was not forced into the throat or lands.

[the possum]

Interesting article, mkl. Thanks for posting it.

Re: enough throat for bullet room-
That makes me wonder if that's why the factory rounds I have use a stepped/belted bullet. So the nose is smaller diameter, in case of a tight bore...

Is there any way to tell when you've got the proper diameter bullet, by simply forcing various sized ones down the bore? I.E., if I loaded some squib loads with various bullets & fired 'em into water, is it easy to see if the bullet squished to completely fill the lands? Or do ya pretty much have to fire normal power loads & just watch accuracy?

[chris in va]

if I loaded some squib loads with various bullets & fired 'em into water,

Bad idea, no underpowered loads.

[Rangefinder]

Quote:
if I loaded some squib loads with various bullets & fired 'em into water,

Can't remember who off the top of my head, but I think it was Snuffy that mentioned something about casting a bullet in dead-soft and firing it into a 55-gal drum full of water. The charge was 1gr. Red Dot if memory serves--just enough to ensure a push all the way down the bore and out. You might find it with a search on slugging.