I ain't doin' that...

[AbitNutz]

I know this might not be the usual reloading subject but I'm a little surprised at the response I received from the people who know about these things.
I have a beautiful Finnish M39 built on a Remington receiver. (if you like ugly rifles, that is) It's in great condition, wood, bore, all over. So I decided to shoot it. I've had it forever but never shot it. For whatever reason, I stuck my Garand bore wear gauge in the muzzle, expecting it to be swallowed by its .312 or so diameter bore. Doink, doink...it would hardly go in. This thing would barely accept the tip of the gauge. So after much head-scratching, and miking my gauge. I decided to slug the barrel...what a pain in the butt. This barrel comes out as a tight .308, more like a .3075.
I check the barrel markings and it is a genuine Finnish marked barrel, SA stamps all over it, dates are correct. The serial numbers match. The serial numbers were re-stamped because that's what the Finns did when they made these rifles. So I start asking questions to the folks who know about these Finn M39's and they say "Oh, yeah they all run small like that. It's fine".
What? I'm supposed to shoot what could be a .312 bullet down a .3075 hole and feel ok about it? I don't think so. I hand load, obviously, so this isn't a big deal but really? Would you guys do it? I mean a couple of thou is one thing but we're talking about, well, more than a couple...

 

[Joeg26er]

What do your bullets mic at?

 

[AbitNutz]

The loaded stuff is at .312

 

[rancher5]

As a Hand gun guy, you order let's say 9mm, .355 - .357 they shoot fine, some people prefer one over the other, or they have a tight barrel, definitely go for it, what could possibly go wrong.

 

[AbitNutz]

Goes right along with, "Here, hold my beer", and who can forget, "Hey, watch this!"?

 

[slowworm]

If it was me, I'd start with a decent 308 bullet. I would note that my RCBS 7.62x54R dies came with 2 expanders, one for 308 and one for 311 or so. Finns seem to be a genuine 308 bore. This is common knowledge on the Mosin forums, or at least it used to be 15-20 years ago.

Damn, I've been doing this a long time.....

 

[jakelly]

CZ chokes some of their barrels that much, and reportedly, more. I’ve heard of .007”, but I’ve not measured that myself. I would start with a .308 bullet, easy fix.

 

[AbitNutz]

I agree it's an easy fix if you handlaod, and I do, and I will. I'm not going to shoot .312 or even .311 jacketed bullets in this rifle. What I'm saying is, the ammo I bought has a diameter of .312 and nobody seems a bit concerned about blowing it down a .3075 barrel. I have to admit that I am not an expert in this field, having never blown up a rifle. However, doesn't this absolutely raise the pressures beyond what the ammo manufacture intended?

 

[CMP70306]

As I understand it the Finish rifles all have .308 barrels as opposed to the standard Russian .312 bore. In my brief research a few years ago it was generally accepted that Russian ammo was fine to shoot in the finish rifles and does not increase pressure enough for it to be a concern.

 

[Texasflyer]

Just think of it as a gun powder fuelled bullet swager with some serious velocity.

 

[AbitNutz]

As I understand it the Finish rifles all have .308 barrels as opposed to the standard Russian .312 bore. In my brief research a few years ago it was generally accepted that Russian ammo was fine to shoot in the finish rifles and does not increase pressure enough for it to be a concern.

Yep, that's what I keep hearing. I just can't quite get comfortable with that, especially with what could be steel-cored ammo. Maybe steel-cored ammo doesn't make a difference, but I would think it would.
At the very least, wouldn't such oversized bullets cause excessive wear?

 

[CMP70306]

Yep, that's what I keep hearing. I just can't quite get comfortable with that, especially with what could be steel-cored ammo. Maybe steel-cored ammo doesn't make a difference, but I would think it would.
At the very least, wouldn't such oversized bullets cause excessive wear?

The steel core should be significantly smaller than the actual bullet diameter so there should be no concerns about it actually touching the rifling.

As for wear the majority of it is due to the heat and pressure of the powder burn rather than the copper.

 

[AbitNutz]

It still seems wrong to fire a .312 projectile down a .3075 hole.

 

[Liberator52]

Been done millions of times. You load, your rifle, your choice.