Moreover, the 5.45x39mm rifle projected by the AKS-74U cannot shoot an initial velocity of 900m/s on the short barrel. Only 735m/s. The small-diameter rifle projectile cannot rely on high speed to achieve the rolling kill effect, and the recoil, muzzle The noise and fire light have increased significantly. Instead, the SR-3 small assault rifle fired a large and heavy 9x39mm rifle. It was originally subsonic, the speed was not enough to replenish, and the amount of shot was less. It could basically burn in the short barrel. The muzzle noise and recoil are well controlled. It is tailor-made for short-barreled rifles.