Clips for use with projectiles and projectile stacking systems in which individual projectiles are clipped together to form a stack are disclosed. The projectiles may be joined individually by a user before loading in a barrel, or during a loading process assisted by features on the breech of the barrel. The tail of each projectile includes a set of clips which engage the nose of a trailing projectile in the stack. Projectiles may be withdrawn from barrel and unclipped as required by the user.