Mosin hand loads

I got a 1940's mosin a while ago, and can get acceptable groups with PPU factory ammo after some battling with the janky trigger.
So far as I can tell, the rifle and barrel is original, and in pretty good condition.
There seems to be some debate about projectiel choice for the mosin, with diameters ranging between 0.308 and 0.312, even in some handloading books
Would I be safe loading some 0.310 projectiles in an original barrel, or better to play it safe with 0.308?
Or do I need to slug the barrel to make sure?

Nominal bore is .310, however there's a poor range of projectiles available. Try using .308 flat base, you will need to exchange the expander button for a 308 one. I have a mosin carbine that shoots 180 gr round nose .308s into 1
inch. Thats better than factory ammo.

To get the best out of a Soviet Mosin, you need to slug the bore and use the bayonet.

As Marty has said, nominal bore diameter is .310. Use a flat base (Mosins need a long bearing surfaced bullet) .311 174 or 180grn bullet. My favourite is the Sierra 180grn Pro-Hunter, but have fun finding those at the moment...

All M91/30s and M44s were sighted from the factory (and after any refurbishment) with the bayonet in place at 300m with the sights set on 300m. Without the bayonet, the groups will print high and to the right, and about double the group size. With the bayonet mounted, it should be around PoA/PoI and around/better than 4 MoA.

Image from a Soviet book

Huh, I didn't realise what a difference the bayonet would make. It will be intersting to see what my local RSO thinks when I show up with that attached.
I'll have a go at slugging the barrel, but I have heaps of 30cal projectiles I might try in the meantime