Abstract: A weapon conditionally activates a cartridge. The cartridge has a projectile and a first mechanical feature. The weapon includes an activator and a station. The activator includes a second mechanical feature. The station positions the cartridge so that the first feature opposes the second feature. On condition that the first feature does not mechanically interfere with the second feature, the activator activates the cartridge to launch the projectile from the cartridge. On condition that the first feature mechanically interferes with the second feature resulting in an excess head space, the activator is inhibited by the excess head space from activating the cartridge.