M16a2 reciever
 

Im wondering, is it labeled "semi safe auto" or "semi safe burst."
Had a m16 out o the armory, an general motors make. The whole upper was a2 but the reciever said "auto" not burst. Wondering if we have an a3 in there or if auto means three round.

Most of the ones I see around here say burst, but I don't get much opportunity to see them up close. My C7 says auto, but then it actually is. Could be manufacturer's variation, a receiver that was diverted from one line to another - I've been collecting guns long enough to know there are exceptions to every rule.

Along the same lines I'm wondering what a Colt Factory four position lower looks like. I know they have prototypes with four position lowers and the fire selection parts are out there...Be really interesting to test in real life.

Got a photo of this 4 position lower?