I have a mosin nagant
"M39 FINI AND 7.62X54" Stamped on the barrel behind the front sights. There are SAKO markings on the barrel and stock.Is there anyone who can help with the final ID as there are other markings which I have seen on the web but not together. I have pics if anyone would like to see them.

That rifle was either made or re-worked in Finland. It is by far one of the best of those M/N rifles. It is my understanding that the Fins rebarreled these rifles with barrels having a .308" groove diameter. But Russian service rifle ammo can still be used in them despite having slightly larger bullets. But if you start reloading for it, use regular .308" bullets. It should be a very accurate specimen of that rifle design.

Finish M39

Military accuracy standard was 1.3" groups at 100 meters and the Sako made ones should be .308 bore as stated and marked SKY............Harold

The standard bore diameter for the M39 should be .3095, so .311 bullets may very well shoot better than .308 bullets. Especially if the bore has any wear to it at all.

But not necessarily... .308" bullets shot in 7.65X53mm Argentine Mauser

Strange things do happen from time to time, but a .308 bullet is under size for the 7.65 Argentine. The original military loading used a .313 diameter bullet. That group or rifle may be the exception, but most Argentines would shoot better with a bullet of proper diameter.

You'd think, but reality is completely different.
1903 Springfields tend to have grooves much closer to .310" than to .308" yet shoot .308" bullets remarkably well.
Swedish mausers, often considered to be at the summit of accuracy for surplus firearms shoot a .264" bullet through a barrel with a .266" or larger groove diameter.
Swill 1911 rifles have grooves very close to .310" and shoot .3075" bullets.

Have you slugged those bores or are you depending upon the net for your measurements? I haven't slugged my Swiss 1911, but I have two of my K31's and the both pretty darn close to .308. As far as I know Swiss GP11 ammo is loaded with a .308 bullet diameter. That's an entirely different story than the Argentine. You can't always take the name of the caliber or information on the net for facts.

Also if you have a Swede 1896 or 38 with a bore diameter of .266, you've got a very worn bore. The rifles were never manufactured with bores that large.

As far as the Springfields, you will find some .310, but the government standard was .308. At least that's fromMaj. General Julian Hatcher's book.

Yes, in fact I slug all of my bores since I shoot a lot of cast bullets.

My 1911 rifle is 310" across the grooves.
K31-s are tighter and usually have .298-299" bores and .3075" grooves, all of mine uniformily have this dimension.
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You are correct, Swedish mausers were never made with .266" bore diameters, is one did have a bore diameter of .266, it would most definately be worn to a smooth bore. Luckily, rifles don't wear out that way, they wear out from throat erosion and muzzle wear.
Swedish Mausers- I have 8 of them, I haven't slugged the 'new' Husqvarna that I recently bought, but the rest of them are .265-266" across the grooves. My M41B is .266" across the grooves and will easily shoot 3/4" 5 shot groups with140gr SMKs(cast loads are a different story), if its worn out, I'd love to see what one of these would do with a new barrel
Sprinfields- I have a 03A3 that is luckily to me closer to .308 in the grooves (.3085") but its also a 2-groove.