Originally Posted By gunny60:
What would keep it from seizing up in the upper?
Hard anodizing on both surfaces, and lube. I have a JP semi carrier in one of my rifles. Can't say I see a particularly noticeable benefit, but it does work just fine. I think you must use a reduced power JP hammer spring with these, tho. I know the semi for sure, but don't know about the '16 carrier.