The FP-45 was a crude, single-shot pistol designed to be cheaply and quickly mass-produced. It had just 23 largely stamped and turned steel parts that were cheap and easy to manufacture. It fired a .45 caliber pistol cartridge from an unrifled barrel. Due to this limitation, it was intended for short range use, 1–4 yards (0–5 m). Its maximum effective range was only about 25 feet (7.6 m). At longer range, the bullet would begin to tumble and stray off course.