Hammy, They are accurate. I've fired a Finnish 91/30 that was just as accurate. The Finn rifles are generally tighter in barrel dimensions than the Russian guns. However, M39s generally are not as tight in the barrel as are previous Finn models (M27,28,28/30).
Accuracy will also depend on how good the ammo is that you are using.
After buying a M39 and taking it to the range for testing, I was so impressed I bought more.