Both hand loads and factory loads. Both will only cycle two, sometimes 3 rounds. I loaded per Lyman book for the powder used. I used H-110 powder. Also used the carbine chart.
Ok on the .750". Wasn't thinking. You are right. All the adjustable gas block will do is restrict rather than open it up.
I have read that the Lyman reloading book is a little conservative. I am also loading light and will work up. However, the factory loads do the same thing. I've also changed magazines, both steel and Magpul. Same results. The gas block is pinned in place, so it can't really be off. Gas tube only pins a certain way also. It does cycle the first round, but after than no. I've never seen this before on any of my other AR's.
What exact loads are you using? The supers may well be just too light, and H110 is not ideal for subs. It'll work fine in a pistol gas system but probably not in carbine gas; you'll probably be restricted to using 1680 or slower powders for that.
Do swap your BCG with a known good one, as recommended above.
