"Hex" receivers do not make a finnish action, the markings and stock make a Fin.
Yes, Russian / Soviet receivers were hex profile until the adoption of the M1891/30 in the early 30s, when officially a cheaper to make round form was adopted. However, Tula and Izhevsk arsenals had huge quantities of the older form in stock and took until WW2 to use them up. You see rifles dated as late as 1940 or 41 with the hex form.
Finnish rifles have tighter bores than the Russian ones. All Finnish rifles use Russian manufactured actions which they inherited on secession from the USSR in 1917, from rifles they were given by the Germans that had been captured during WW1, or were captured from the Red Army in the 1940/41 'Winter War' when the Soviets invaded the Karelian Peninsula. So most Finnish rifles have hex receivers, but you also find rebuilt Soviet M1891/30s too with round reciever bodies. As BohemR13 says, the stock is the main giveaway, hex reciever models restocked in Arctic birch with a two-piece forend where the two sections join with a really neat dovetail joint. The Finns usually stained the timber with potassium permanganate that gives it a really dark appearance, while Russian / Soviet examples are light-coloured birchwood with a fragile shellac type varnish finish. M1891/30s were only changed slightly from the Russian form, the dark wood and lack of a foresight hood-protector being the main giveaways. Earlier Finnish rifles only retained the Mosin-Nagant action and the barrel, stock, sights, sling fitting etc are all different (and better). The SAKO rifle building facility was created specially to do this work and is the ancestor of today's Sako company.
Lapua produces .310 123gn FMJs (designed for the 7.62X39mm AK round) that shoot well in 7.62X54R with powders in the Viht N135, H4895 range if you can find any. Other .310 light bullets from the US manufacturers will do too. In the heavier bullet field, look for bullets usually made for the .303 British or 7.65X53mm Belgian / Argentine Mauser, 7.7mm Jap etc. The top of the pile accuracy-wise is Sierra's 174gn HPBT MatchKing, and Hornady makes a .310" FMJBT of similar weight. Hornady and Sierra make 150 and 180gn flat-base PSP hunting bullets too for the .303 etc if my memory serves that can shoot well in the 7.62X54R. (We aren't allowed expanding bullets in the UK except by special permission for hunting use and so can't buy them for target shooting, so no experince there.) 0.308" bullets are worth trying, but they usually don't shoot well in Russian rifles, but will in Finnish (SAKO made) barrels that are much nearer .30 cal. Powders wise, anything that works well in .308W suits the 7.62X54R - Viht N140, N150, H4895, VarGet, Re15, IMR-4064 etc. Some loading manuals have data - Sierra, Hornady, and Lyman, although you can usually substitute .308 Win data safely that is only slightly lower despite the 7.62's larger case. Loaded up, the 7.62X54R is a match for .308W both ballistically and accuracy-wise, although the M-N rifle and its terrible trigger pull rarely allows you to prove that. The USSR dominated Olympic Running Deer events for many years with the cartridge in specially built match rifles, and it still performs well out to 800M range with specially manufactured sniper ammunition in Russian military service in the SVD Dragunov semi-auto rifle.
Laurie,
York, England
