Mosin Nagant slugs to .308 - really?

[dstrout]

Hi all! NEw member here. I've been reading for the past few weeks, but this is my first post.

I got a 1942 Izhevsk MN. Shooting winchester softpoints at my 50 yd range, I was getting groups in the 1.5 - 2 in range, which is about as well as I can do open sights on my benchrest .22.

Of course, then next step is a scope and handloads. I've loaded before, but only 45 ACP, never rifle.

Anyway, long story, but I slugged my bore and came out at .308. I tried it twice from the chamber and once from the muzzle, and got the same thing every time. Can that be?

Slugging really is just "pound fishing weight that is bigger than the barrel through the barrel with a wooden stick and measure what comes out", right? The .308 is the outer diameter of the output. I didn't measure the diameter at the grooves, but they are well defined, and I could feel the slug turning as I pushed it through, so that seems good.

From what I have read, I should be seeing .310-.314. Am I doing something wrong, and if it is .308, does that make it special in some way (i.e. more valuable than the other million 1942's out there). I trust my calipers - they read the winchester as .308, and a 45 cast at .451, so I don't think its a calibration issue.

Any thoughts?

thanks,
Dave.

Information

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[HOOKED ON HISTORY]

Look for SA marks? The Finn capture /reworks often have tighter bores.

[fernleaf]

Look for SA marks? The Finn capture /reworks often have tighter bores.

The only Finn Mosins with .308 bores are the M28-30s, all others have a nominal .3095 or .310.

A .308 bore on a Soviet wartime M91/30 is strange - is the bore in particularly new condition? It certainly doesn't add any value. I would stick to handloads using .308 projectiles, or shoot Norma ammo, which is loaded with .308 bullets.
Perhaps you could try a few rounds of lead core ball and see if you get any horrible pressure signs - I'd avoid steel core ball.

[dstrout]

Well, it looks like I can't run a caliper. I took a marker and colored the groves to make sure I wasn't dropping one side of the caliper into a groove. Turns out I was. sigh. It slugs out at .312 if you actually measure correctly.

sorry for the waste of time!

[HOOKED ON HISTORY]

sorry for the waste of time!

The only dumb question is the one that is not asked.
Helpful folks here.

[bearrowland]

Welcome aboard Dstrout!!

[mbogo3]

Finn 27's can also be .308