Given how common the Mk(b) still is, it might be wise to give sovjet assaults drum magazine's and select-fire straight up for their ppsh's to even the playing field out a bit. In general, I think it might be good if weapons were rebalanced so that additional weapon levels give only largely cosmetic changes instead of actual stats changes, I believe this would help balancing several weapons enormously AND would ease the frustrations of new players facing veterans of untold hours of gameplay.