Mosin Nagant inaccuracy with hand loads and chamber dimension differences

[Hang Fire]

I was given a box of hand loads done in new Norma brass for 7.62x54, of which five had been fired. The guy told me his Soviet MN 91/30 was so inaccurate with hand loads, he had gotten rid of it.

As I don’t shoot other people’s reloads, I pulled the bullets. The J-word’s miked at .308”, the inside diameter of the fired case necks was .314, so small wonder his MN was inaccurate with the hand loads.

I decided to use the five fired cartridges for a little dry fire practice, but that didn’t pan out. The chamber difference between the rifle they were fired in and my two MN was so great, that no way could they be chambered. (On my M39 Finn, the groove diameter slugged at .311”, on the Tula carbine at .3145”)

To double check, I neck sized a couple of the fired cases, but result was the same, no go. So set up side by side on a flat metal plate and even to the naked eye, the fired case’s shoulders were seen to be stretched much more forward than on unfired cases and some empties fired in my two MN.

[Hardcast416taylor]

Well, at least you have some good componets now once you pull the .308" bullets. This is another example of starter loaders not knowing about bore dia.Robert

[handyman25]

I would not reload the cases I would recycle them. If the rifle that they were shot in had head space issues then the brass now has these issues. Not common to be sure but not worth the risk to same a few cents.

[leadman]

It is easy to check the case for impending head seperation. Use a paper clip that it straightened out and put a little bend in one end. I like to sharpen this end. Then run it in the case and put the bent tip against the area of the case in front of the base and pull out slowly just a little bit. If the case is stretched too far you will be able to feel it.
I can actually measure the case in this area with my RCBS Casemaster with a dial indicator.

[ShooterAZ]

Don't toss the brass! Norma brass is excellent stuff, and if was new to start with you should be fine to FL size and start over. Once you do this and fire form to your chamber, set the dies to neck size only and your brass will last for a very long time especially with cast boolits. Using j-bullets I go with the .311 or .312 bullets made for use in the 303 British. .308 will work, but as you have found it doesn't always give the best accuracy in the MN. For cast boolits I have found that the Lee C312-155-2R work well in my MN. 16-18 gr. of 2400 you will find a sweet spot.

[Thumbcocker]

I have a Finn that has a much tighter chamber than the Russians. My brass swelle ahead of the rim where the shell plate prevents it from sizing. FWIW.

[Hang Fire]

I have a Finn M38 with Sako barrel, I keep it's brass separate from the Tula's.