A projectile (10) comprises a cylindrical body (12) with a first (leading) end (14) and a second trailing axially opposed end (16). An internal cavity (18) is formed between the ends (14 and 16) and holds a volume of propellant material (22). The first end (14) is closed by a nose (20) that is fixed to the body (12). The end (14) is sealed with a base seal (26) that seats a primer (24) for igniting the propellant (22). The primer (24) is located inboard of the second end (16) and the base seal (26) to reduce the likelihood of accidental activation. Seals (30) are formed about the body (12) for maintaining gas pressure of deflagrating propellant. The seals (30) may be formed integrally with the body (12) or separately from the body (12) and seated in respective grooves (40) formed circumferentially about the body (12). Also disclosed is a breech sleeve (810) shaped to complement the breech of the weapon and a throughway (816) defined by an internal surface, the projectile being able to pass through the throughway (816).