Okay, I finally got out and shot 200 rounds of the Maylaisian ammo; 1986 lot 2. the first 150 rounds I fired with no issues. The first 50 was in short burst, the second 50 was one burst, and the third 50 was a mix of short and medium burst with no ammo issues. I then changed barrels and tried another 50. About 15 to 20 rounds in I had a case separation. I cleared it, changed back to the other barrel, and fired the rest of the belt with no issues.
While looking for the separated case head, I found a case that had a line around the case and a pin hole in that line, and I believe that case was close to separating when it was fired; I also believe it came from the second barrel, based on where I found it, and before I finished the last belt.
All the barrels used have had the head space checked to that bolt with Foster go/no go Gage's in the past and all showed to be within tolerances. I checked them again when I got home, and the barrel that had no issues did have a shorter head space, than the barrel that had the separation.
I think if your going to shoot Maylaisian ammo your going to need a tight chamber in order to avoid case separations.
While I haven't had a chance to compare the brass with NATO brass, the wall thickness of the brass that separated did look thin to me. But at this point that doesn't mean anything.