The difference between the various M39's is who mounted the barrel on it. Sako, VKT, Tikka, and a Belgium supplier are the main suppliers. The Belgium supplier is identified by a "B" stamped on the barrel shank
And the B barrels have the odd distinction of some rather interesting color variations on the barrels. I've seen bronze, red, reddish/purple. Somehow happened during the bluing process. I've heard several theories why but I'm not sure which is true.
Of the M39's, B-barrels, Tikkas, and the "Sneaks" were probably all assembled post WW2. So I doubt the B-barrel saw any WW2 action. I have 6 M39's and my B-barrel is the most accurate of them all. All are sub 2 MOA rifles.
And the B barrels have the odd distinction of some rather interesting color variations on the barrels. I've seen bronze, red, reddish/purple. Somehow happened during the bluing process. I've heard several theories why but I'm not sure which is true
it is because they used a higher nickel content in the steel.most all I have seen are a plum color.
pete