I think R6601 lowers are great starts for M4gerys. Even better, they look great on R6721 projects, since the R6721 is an Hbar. The worst part about the lowers in that range is that they usually had the sear block held in place with two really, really big pins from both sides. Not to mention the already annoying oversized firecontrols. Other than those two things, I think they are great.