Blow-forward is a firearm operation type where the friction and pressure of the bullet traveling down the bore drag the barrel forward. This forward barrel motion provides most of the energy required to eject a spent cartridge case and chamber a fresh round.
Blow forward Wikipedia
In Blow-forward, the frame incorporates a fixed breech face and the barrel moves away from the breech (frame) during the cycle of operation. In contrast, blowback firearms have the frame fixed to the barrel and the breech face moves in relation to the frame. The breech face is a part of the moving slide or bolt, depending on the layout of the blowback firearm.
Due to the reduced mass of rearward-traveling parts coupled with the increased mass of the forward moving parts (barrel in addition to bullet and propellant gasses), recoil energy is significantly greater than other operating mechanisms. The barrel and spring are generally the only moving parts. Most blow-forward guns rely partially on the inertia of the barrel as the rest of the firearm recoil away from it.
The first blow-forward firearm was the Mannlicher M1894 pistol. The principle has been used in a few other weapons, including:Schwarzlose Model 1908
Hino Komuro M1908 Pistol
Mk 20 Mod 0 40mm automatic grenade launcher.