BB (ball bearing) guns are compressed air powered guns designed to shoot a metallic sphere similar to a shot pellet. Although not powered by gun powder, the projectiles still have significant penetrating power. The muzzle velocity of such weapons can be as high as 360 m/sec (traditional gunpowder pistols range from approximately 220 - 440 m/sec)1. There have been many published cases of soft tissue and even intra cranial penetration in the literature1,2,3. Measurement and composition can vary but most BB projectiles measure 4.5 mm in diameter and are composed of steel covered in zinc or copper to resist corrosion4.
This patient was unaware that he still had the BB projectile embedded in his arm. He had been shot in the arm at close range as a child and had believed that the bullet had just deeply wounded his skin and rebounded away. He had a small scar on the skin overlying the location of the foreign body.
This case serves to highlight the importance of considering plain radiographic imaging in patients with skin damage from BB guns even if there is only a small wound and the patient is unaware of a penetrating injury.