MiniZ -
OK thanks. I was hoping someone made such a thing; the magazine adaptors always looked like a kluge to me. Maybe we will see more and better stuff with the capacity restrictions gone.
In the event that I can only get a .223 lower, I was looking for a larger fire control pin type, since I already have a .170 match trigger set. And it seems that stripped Colt lowers don't seem to be too common.