The PIAT was based on the spigot mortar system, and projected (launched) a 2.5 pound (1.1 kg) shaped charge bomb using a cartridge in the tail of the projectile. It possessed an effective range of approximately 115 yards (105 m)[3] in a direct fire anti-tank role, and 350 yards (320 m)[3] in an indirect fire role. The PIAT had several advantages over other infantry anti-tank weapons of the period; it had greatly increased penetration power over the previous anti-tank rifles, it had no back-blast which might reveal the position of the user or accidentally injure friendly soldiers around the user, and simple construction.