[LDBennett]

My Mosin Nagant is a HEX receivered M91/30 with a 30 inch barrel. We think it is from the mid 1930's.

I'm reloading for it and am confused as to what the bore size is?

The Hornady manual shows loads for both .308 and .312 bullets, with the .312 bullets suggested for guns that were imported recently (cica 2003), slightly before the time my gun may have been imported. My gun was sold by Big Five Sporting Goods stores in CA. in about 2004 or 2005. But the 308 bullets will not drop into the bore and the land to land measure, as close as I can measure it, is closer to .308 than .312. The Hornady reloading section is labled 7.62 Russian (7.62 x 54 R) (7.62 x 53 R) furthter complicating the mystery for me. Any other reloading manual that I own and happens to have loads for 7.62 x 54 R only list .308 bullets.

Add to that, the Winchester white box commercial ammo I have been shooting measures about .310. If the bore is indeed .308 what was the .310 ammo doing to the pressures? I think there have been no signs of excessive pressure so far.

So what would you expect for the bore size on a HEX receivered M91/30 from the mid 1930's that at some point may have been refurbed (barrel still about 30 inches)?

LDBennett

 

[Denny]

LDBennett, to find your bore size you could slug the barrel and measure. Denny

 

[chasdev]

You will probably find your bore larger than .310.
I've measured several at .313/.314....
Get some lead fishing weights (I know,solid balls are better) buy a 3 foot hardwood dowell and cut it into three pieces.
Load the lead and bore with grease and tap the lead into and through the bore from the muzzle end.
Measure the result and you will find the TIGHTEST part of the bore.

 

[7.62x54r]

http://7.62x54r.net/MosinID/MosinSlug.htm

 

[jjk308 In Memoriam RIP]

I wouldn't slug it by going all the way through. Even greased if there's any roughness you'll lose lead and get a too small diameter, plus theres always a chance of a jammed slug followed by urgent posts in The Workbench.

Going in a few inches beyond any muzzle cleaning rod wear is plenty, then knock it out.

 

[7.62x54r]

I've slugged dozens of bores and only had one get stuck. There was a crater on the side of the barrel and I forgot to grease the slug. I don't agree that you'll "lose lead" to any extent that it changes the final dimension of the slug.

 

[chasdev]

Say what?!
As long as you stack short sections of dowell and the dowell fits the bore correctly, there is NO WAY to stick a lead ball in the bore.
If the bore is so rough that it will eat up the slug, why bother slugging it anyway?
I HAVE slugged frosted/pitted bores and it's goes easier, because the bore is larger and compresses the slug less.

 

[jimlay]

I wanted to try that split shot lead fishing sinker trick. I went to Wally world and checked their sporting goods department. Guess what? No lead. It looks like lead, but it ain't lead. They had a butt load of sinkers and nary a one was made of real lead. Thank the trial lawyers, I guess.

 

[7.62x54r]

I wouldn't use split shot, you need an "egg sinker". I haven't looked at WalMart lately, but I bought several packages a while back so I'm probably good to go. I generally tag and save them for future reference, but it would be easy enough to reshape them to a larger diameter and use them again.

 

[AMMOe]

I think you'll find that the nominal groove diameter for Finn rifles until the Model 28's was .310. I can't be sure of that but I seem to remember reading that. ~Andy

 

[7.62x54r]

http://7.62x54r.net/MosinID/MosinSpec.htm

 

[LDBennett]

7.62x54r:

Well I slugged my Nosin Nagant m91/30.

You have to be very carefull about buying sinkers as not all are lead. And those that are lead seem to be a pretty hard alloy. It took some fooling around but I found a "bullet" sinker that would start and go through the bore and leave meaningful markings on itself. Several slightly larger ones would not even start and appeared to be harder lead than dead soft lead as used for swedged bullets. I think I'll search out some pure lead wire as used for bullet swedging for any future slugging. But I got it done.

Next problem: Calipers and their accuracy. I have two calipers, both digital and a set of micrometers with "standards" for calibrating the mics (1, 2 & 3 inches exactly). My good $125 calipers read very accurately when tested on the standards but the $25 ones from Harbor Freight are 0.002 inches too small in their reading of a 308 bullet and a good 0.001 inches off on all the standards. (Yes they were zeroed!).The cheapy calipers are junk. Don't buy them if you expect to make any accurate measurement to the nearest 0.001 inches.

My barrel slugged .302 for the bore and .314 for the grooves. I guess the 308 ammo I made up may not be accurate. They are already made so I might as well shoot them but it looks like the right bullets are the .312's as used for 303 Brit.

Thanks for the article. It helped. But now I'm sad cause I know the accuracy testing I planned will probably go badly. Oh well, that's life!

LDBennett

 

[7.62x54r]

You have to buy the egg sinkers from China. Then you're assured that they're lead.

 

[LDBennett]

The Chinese seem to put lead into everythng they ship to us!

Maybe its a conspiracy to eventually give the USA populace lead poisoning to bring down our defences to their takeover of the world?

LDBennett