Surprised to see Colt and LMT lumped in with POF. POF started life as Pakistani Ordnance Facility. Nuff said..
Anyhow, I had a very costly Ka-boom holding a Colt LE6920 one day. All I can say is I was quite grateful for Colt's QA, cause if their QC wasn't there I might not still have all my fingers or sight in both my eyes.
Problem was an over pressure cartridge from a poorly crimped neck. Bloated out the upper and seized the BCG. The lower was fine, and the BCG just needed a good cleaning. I still use it today. The upper was toast though. It sits as a reminder on my work bench now. Tells the story that using guns requires your constant and undivided attention.