The is a screw just below the barrel on the comp and weight the screws into the barrel shroud or whatever you want to call it.

I expect the comp that blew off the gun had not been secured or had come loose. If it were loose and moving around a bullet exiting the barrel might have blown it right off. I can't see any other way that could happen.

I'll try to take some pics of the comp.

Thanks SmithNut for the brochure.