time to wade in and show just how little i know- it was the CALCIUM CARBONATE in the powder that was used as a preservative that caused the bolts to weld themselves shut in the m16- that and too tight a chamber tolerance - a savvy armourer or gunny would take a piece of crocus cloth, wind it around a cleaning rod, chuck the thing in a drill and polish the heck out of the chamber- they didn't fail after that- either that or the casing would fail due to the higher pressure and extract the head of the case only, leaving the rest inside- this is all well documented over on the ar boards- think it's called "the truth about the m16 " or something like that- it's like over 4 pages long and extremely well written by a guy that was heavily involved on the technical side
back in 1990, colt was offering a "special" - you know how they were for boxed "specials"
ar15a2( std barrel) sporter with a2 sights-even though the manual said that these only came on the h-bar,bayonet( m7) 2 -5/20 magazines, and a scope mount - the dealer added an armscorp 3x9x32 and rings ( they also included that piece of nylon strapping they called a sling) for 1100 canadian- i still have the receipt and the gun