MN Bore size?

[Nora]

I was over haunting 7.62x54r.net looking for any possible new info. In the Specs section they have the groove diameter listed as being .314 on purpose. If this is the case then mine is normal and not over sized. Being the only place that I've seen this listed as the correct size does any one else have a point of reference that would back this up? Also, if this is true then why aren't molds made as a standard size to accommodate it?
http://7.62x54r.net/MosinID/MosinSpec.htm

[Stoats]

Anywhere between .308 in a Finnish one to around .314 is "normal". The Russian specification calls for .310 or .311 depending on which source you consult.

[mike in co]

big difference between normal, commom and spec.
fin spec is 310 except the few early 308's
russian an dothe comblock versions have been reported up to 316 or so.

mike in co

[Calamity Jake]

I was over haunting 7.62x54r.net looking for any possible new info. In the Specs section they have the groove diameter listed as being .314 on purpose. If this is the case then mine is normal and not over sized. Being the only place that I've seen this listed as the correct size does any one else have a point of reference that would back this up? Also, if this is true then why aren't molds made as a standard size to accommodate it?
http://7.62x54r.net/MosinID/MosinSpec.htm

American factory made molds are made for American made guns(.308)

Lyman 314299, if Lyman made it big enough to began with, will work pretty good.

[leadman]

If you can't find a mould that drops a large enough boolit you can lap out a Lee pretty easily. If you ruin the mould (hard to do) you aren't out much money.
Custom moulds are an option also, but a little pricey.

[pbbutz]

My 1937 Tula 91/30 slugs at .313. I'm thinking paper patch.


Butz

[Nora]

I've got several MN's with the largest being .303/.314. It also shoots well when feed properly. I just have never seen any reference to the bore size that is "suppose to be" .314 before. That's my question, is to the validity of their statement.

[Oldeyes]

"Supposed to be" can be interpreted in several ways. The "official" specs for the 7.62x54R are .300" bore, w/ .310 groove diameter. The military tended to modify those specs a bit for battlefield reliability- generally by adding three thousandths to the groove diasmeter to make up for fouling in the field. This seems typical of European army practices...
So, Russian military specs are normally .313 groove diameter in the pre war produced Mosins, up to .315" in mid war units (WWII) So an average would be .314.
Where did I come up with this info? I own about 125 Mosins of all flavors, and this is what I have seen over time. I have encountered a few Russian 91/30s in the .311 range, as well as some worn examples at .318. (Tired would be a gentle description of those!) On the other hand the Finns tended to produce tighter barrels with my minimum being a .308 in a P-26, .3085 in a pair of 28/30s, and .310 in my minty M27s and M39s, with groove diameters going up with wear. Oddly my Finn made Tikka M91-30s duplicate the Russian specs at .313. Go figure!
As to other variants, most w/ minty bores have been in the .313 range, which include my Polish, Romanian, Hungarian models. I've never checked my Chinese 53s, maybe someday?