A method of firing of arms which utilizes both action and reaction forces in the process of firing. The action force propels the projectile (14) while the opposite in direction reaction force is used with an independent freely moving inert mass (20) in which a cartridge case (18) resides. Since the movement of the inert mass (20) does not affect the position of the barrel (12) prior to the projectile (14) leaving the muzzle, the barrel (12) remains steady during firing, thus achieving very high accuracy of shooting.