When I have the chance to interview Jim Sullivan, one of the original designers of the AR15, one of the subjects that came up (not surprisingly) was the record of failures of the M16 early in Vietnam. What was the cause of those problems? The full story includes several compounding issues, including a lack of issued cleaning kits and non-chrome-lined barrels. But most significant, according to Sullivan, was an inexplicable reformulation of the powder in the 5.56mm ammunition. This caused a huge increase in gas port pressure (in the order of 10,000 psi) and directly caused parts breakage and unreliable operation. Here is his description of the situation:
In an unrelated note, it has come to my attention that Apex Gun Parts has gotten their hands on a bunch of parts kits for Spanish CETME-L rifles. These were a domestic Spanish take on the H&K style roller-delayed action, in 5.56mm and using NATO standard mags. They were replaced by the G36, and there was speculation for a while about the possibility of getting kits into the US – well, Apex actually has them in hand now (sans receiver and barrel). It sounds like they have enough to make it worthwhile for parts manufacturers to develop semiauto parts and receiver flats for them (no parts are interchangeable with H&K rifles), so I already placed an order for one myself. The introductory price of $225 for a kit is pretty cheap for something that won’t come back again, and if the market develops a good build solution for them it will be a neat and unusual rifle to have!