My MK18 has recently started to have malfunctions at least once per range session that looks just like an over-gassed system. Empty brass will will come back into the ejection port, primer first, and impinge the round going into the chamber and the bolt. Will typically happen with a specific mag when suppressed, so guessing the spring is about done on that mag (M2 with who knows how many thousands of rounds), but it has also happened with a brand new (<500 round) D60 when unsuppressed.

What has me puzzled is that the barrel only has 3100 rounds (1800 of which were suppressed). Action spring also only has about 2700 rounds on it. That round count seems a little low for the gas port to be having excess gas, so was wondering if others would agree.

Barrel is a Colt 6920 cut down by ADCO with their gas port size adjusted. Buffer is a H2, per the Crane spec. The one other variable is a WMD BCG (put in back when I used to think NiB was "the thing").

Obviously I can try a different bolt (to test the extractor) and put in a H3 buffer, but the intent of my question here was more about port wear, because again, that seems low for this to be popping up now. Thoughts?