Automatic and semi-automatic firearms of remarkably reduced mass yet capable of long-range accuracy because of unique recoil reduction are characterized by (A) a temporary combination of a barrel, an integral breech and a separable chamber that in operation of the firearm is moved by a compressed spring distally before and while a chambered cartridge is fired, (B) run-out of such temporary operative combination diminishes firearm recoil, (C) recoil of the temporary operative combination recompresses the spring and (D) the separable chamber is loaded with a round while spatially separated from the breech and barrel.