Mosin bore sizes

[bob4wd]

I've gathered from reading numerous threads on this site that Mosin bores can be up to .314", so I slugged my sniper to see if it's accuracy might be improved by going to a larger bullet than the .309" lead I've been using. It measures right at .312", so I loaded up a couple each of .312", .313", and .314". All three bulged the case neck, BTW. Before shooting 'em, I tried chamber fitting. No luck, none of them wold allow the bolt to close, although the .312" almost fit, that is I could force the bolt to close if I really pushed it. Ain't about to shoot that one, though- pressures have got o be way high!
So - does anyone have any words of wisdom for me here? .309" is probably too small, being .003" under bore diameter, and the theoretical ideal of .312-.314" won't even chamber. Velocities are modest, I'm using 14 to 16 gns. of unique, so may not be getting full obturation. Beyond trying .310 and .311", which I will do after I order some bullets, has anybody else tried lead bullet loads with success? Or figured out a way around the tight chambering?

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[jmoore]

Or figured out a way around the tight chambering?

You could turn the case necks down a few thousanths.

[Al Diehl]

Or, have your chamber neck opened up slightly to be better suited to your bore and the rounds your are wanting to load. This is what I would do.

Al

[WarPig1976]

I'd try turning down the neck first,,,,, it's cheaper...

You probably already have but are you sure the chamber is completely void of any foreign material?

[Catch22]

OK, this may be a dumb question, but I'm in the learning process. Isn't the standard 7.62x54R a .312 bullet?

Trying to figure out how that size of bullet won't fit if it's chambered for that size.

[WarPig1976]

.3105 is the surplus diameter. Something else is not right as people shot .312 all day long in Mosins. Are you seated too long? If it where me I'd be looking elsewhere. Shine a light down there and use a dental mirror to do a though inspection. Your shooting lead? Maybe you have some nasty lead fouling? Just an odd problem...

[bob4wd]

.3105 is the surplus diameter. Something else is not right as people shot .312 all day long in Mosins. Are you seated too long? If it where me I'd be looking elsewhere. Shine a light down there and use a dental mirror to do a though inspection. Your shooting lead? Maybe you have some nasty lead fouling? Just an odd problem...

No matter how much I learn about stuff, it seems there's always one or two things that I didn't know (or forgot!) that are really important to the matter at hand. Such is the case here. i've been reloading for many years, but mainly using standard components and standard data. Am just now in the past year or two getting into the oddball stuff, like low velocity lead bullets on rifles. These larger diameter bullets are a good example of this. NO published data, other than internet, for the Mosin is for bullets other than .309 or .310, so I'm tiptoeing my way into this.
In this case, having always been taught that overall length should be pretty close to factory spec, I made sure to do exactly that. Didn't take into account that the ogive shape is blunter than fmj military rounds, so the bullet contacts the riflinglong before the round is fully chambered.
The visible bulge was because the bullet wasn't all the way into the neck, and the hard chambering was because the bullet was stopping all forward progress, not because the neck was too fat.
So Warpig, take a bow- you nailed it!
Off to the range in a couple of days with an assortment of 312, 313, and 314. And a lead sled, just in case!
,
.

[WarPig1976]

Thanks, but I'm to fat to bow.. I don't load lead but when I do I'm sure I'll do the same thing! Just one of those things like when I couldn't figure out why I wasn't getting consistent coal,,,and they say it's supposed to be relaxing...

[ptf18]

What lead bullets are you using? I am interested in trying lead as I cant find jacketed bullets for the Mosin Nagants I have.

[Patrick Chadwick]

I cant find jacketed bullets for the Mosin Nagants I have.

I reckon you can - if you look in the right places!

If you can find them try the Hornady 3130 round nose. These have a diameter of 0.312", They need to be seated well in with the case mouth up to the crimp ring. Crimp - no crimp? I just set the die so that the case mouth shows the barest rubbing mark, to ensure that there is not the slightest flare remaining to make chambering difficult. Sierra make a similar bullet with a 0.311" diameter.

In both my 91/30 and a Finnish sniper, the Hornadys turned so-so performance into excellent performance. These round-nose types have a long cylindrical portion, so that the nose engages the lands before the bullet is totally free of the neck. This improves bullet guidance (and reduces gas-cutting).

Boat tails in old service rifles with their often deep throats (compared with modern standards) will come free of the neck long before the nose engages. Since the necessary play between case and chamber means that the case neck is sitting on the bottom of the available space in the chamber. Gas will flow more easily over the top of the bullet, causing the bullet to be engraved slightly on the skew and thus emerge from the muzzle with a slight skew. This cannot be good for accuracy. Again and again I find that good old-fashioned round-nose bullets give the best grouping.