Another shooter, who was nearby when the Kaboom occurred, reported: “I was standing 10 feet behind [the shooter], loading mags. The shot was no different than any other shots. I only looked up because the RO was yelling for assistance.”

Obstructed Barrel? Probably Not: “The target showed four hits — the fourth round Kaboomed the rifle. [If there was an obstructed barrel only three holes should be on the target.] A piece of the exploded cartridge is still in the chamber of the barrel. The barrel extension split into three major pieces with smaller pieces cutting the left inside forearm.”

Suspected Cause? “It was a combination of rifle and pistol powder. The rest of the batch was pulled and there were apparently 3-4 other rounds with mixed loads.” It has been reported that these were commercial .223 Rem reloads.

What Happened to the Operator? “The shooter is fine. He got whacked in the face with the charging handle, giving him a fat lip. Minor cuts on his face. His wrist got fragged with carbon fiber/free float tube remains, which were embedded in his skin for a few weeks.”

Parts Ruined: Upper receiver, Cav Arms MK2 polymer lower receiver, Bolt Carrier Group (total loss), forearm, barrel, gas tube, gas block, muzzle brake, mag release, bolt release, custom trigger and take-down pins. Also charging handle is bent and trigger group sustained some damage.