Diagram of a primer-actuated blowback action (with rotating bolt), before and during firing.
Primer actuated blowback is an unusual method of blowback operation. It uses a normally undesirable phenomenon known about since the earliest unitary firearm cartridges, wherein a poorly secured primer could back out of the case on firing. This is one of the few ways to mechanically jam a revolver, and led to some initial resistance to adopting cartridge revolvers.
In a primer-actuated blowback mechanism, this becomes a deliberate feature of the system: the round is held firmly in place by the action until the primer pushing backwards releases the bolt head.
Examples[]
- Roth machine gun
- Postnikov APT
- M1903 auto prototype
- SVT-40 prototype
- Clarke carbine
- Garand Model 1919
- SMAW spotting rifle
Gallery[]
Schematic of a primer actuated rifle with rear-locking wedge
Schematic of a primer actuated AR-15 bolt (US7886470B1 - Bolt assembly for a firearm)