A projectile for use in a barrel with stacked projectiles, particularly for a weapon which can be reloaded by a user in the field. The projectile comprises a tail assembly. The tail assembly comprises a casing and a closure in the tail assembly, the casing and closure forming a chamber containing a propellant charge, an exit from the casing for release of propellant gases into the barrel when the propellant is ignited to launch the projectile from the barrel, the closure closing the exit, wherein the closure is opened by ignition of the propellant within the chamber, a primer in a leading end of the casing, an inductor around the casing, and a signal detector at a leading end of the casing and inductor, wherein the signal detector triggers the primer and the signal detector receives a signal output from the inductor to trigger the primer.