Hey GRA556-
What twist is your 605? Assume mine is 1:12, snagged it at a gunshow from a vendor I know, for maybe $150.
The gas port is whatever Brownells makes them; as noted, it runs great on one BCG but not another.
Really like mine; like iron sights, and still shoot them pretty well for a codger; appreciate the full sight radius on a carbine.
Thanks,
Moon