failure to feed/eject on Every round

[NugginFutz]

Changing the magazine (any 5.56 mag will do, if loaded to 5 or so rounds) can help eliminate the mag as an issue. If the problem persists, then you obviously need to diagnose further.

An upper with a misaligned or undersized gas system can behave in this way, but more information would be useful to help diagnose the problem (upper issue vs. magazine issue).

Does the bolt visibly move or cycle when fired? (No gas)

Are spent cases being ejected? (bolt travel issue / might indicate low gas)

If so, where are they landing (eg. 3 o'clock at 5 feet)? (may help determine under/over gassed)

Does the bolt lock (all the way) back on an empty magazine? (indicates whether or not bolt is traveling sufficiently rearward.)

Are any rounds being stripped from the magazines? (insufficient bolt travel / sticky mag)

Is the bolt riding over the round? (insufficient bolt travel / sticky mag / weak spring)

Is there any difference in behavior from first to last round? (sticky mag / weak spring)