Weapons like Kriss Vector and AK12 actually stabilize better under full fire than under single fire or burst conditions. So that's not entirely true. And for P90 you mention, similar thing applies. P90 hardly has any recoil because the recoil force goes pretty much straight into the shoulder. Only thing ruining its accuracy is slightly shorter barrel. But it's probably by far the best in class when it comes to such compact weapons. At 10m range, even full auto emptying of entire 50 round magazine should deliver outstanding accuracy. The weapon is otherwise effective up to 200m.