Thread: Curiosity - AR "run out"

Hello there!
Just as matter of curiosity and learning, what can/did cause it?(as follow)

I went for a quick sight in with my hunting rifle and take my AR for a play in between shooting, what happen is, after i fire couple shots i pull the trigger and if fired a little burst of 3 shots as it was full auto, i saw it happening before but was just two shots then.

Can you guys with a lot more acknowledge explain it to me? Follow the rifle specs:

Stag Arms mode6 5.56, 18" bull barrel suppressed, rifle length gas tube, everything original (exception the barrel length), i have fired around 8-900 rounds thru it and only once before it happen, trigger is a 2 stages factory match.

Cheers.

Mac