What boolits are used? Regular 9mm Luger? Or heavy elongated like the 300 BO uses?
And what, exactly, can the 9x39 do that the 300 BO can't?
Myself, I'd like to rebarrel a Marlin 336 30-30 with a 1:7" twist barrel so heavy subsonics can be used. The twist rate of the factory barrel is to slow for much over 180 grains.