Parallel got the fright of his life when participating in a Magpul Dynamics “Dynamic Carbine” course.

Side of upper receiver blown open.

Bolt carrier split.

Bolt face split.

The drill was firing from the urban prone, weapon side position. We loaded and made ready and I waited for the threat command. When the threat command came I went into the urban prone position and fired. On the second round the upper receiver blew apart. It took a few seconds for me to get oriented and realize what had just happened. I checked to see that there wasn’t another round in the chamber and raised my hand to let Travis know there was a problem. Travis was already on the way as he said that he thought that I was on fire from all of the smoke that was rising from me. There was a medic who checked me out real good to ensure that some shrapnel hadn’t penetrated my skin anywhere without my being aware of it. I sustained only minor injuries (a bruise on the left forearm and some flash burn to the face).

…

The 6920 is on its way to Colt Manufacturing for analysis as of this posting. I will certainly post the results of the analysis as well as the resolution when that information is available. I would appreciate it if the wild guesses as to the cause of this failure were withheld until Colt Manufacturing has had a chance to check it out. I will give a few facts that will help to keep the conjecture to a minimum. The barrel was clear before and after the event and the ammo used was factory XM193. I don’t know if the brass was ejected, it appeared to be, however, there could have been part of the brass case left in the chamber, I was too busy trying to get back to training to check, then the gun went via FEDEX to Colt before I had the chance to check because I was trying to catch up on all of the work I had neglected while out running and gunning.

Many thanks to jdun1911 for emailing me the info.