just a quick word about customer support from robinson arms. i recently got my XCR, but i was missing one little set screw for the m4 adapter. i sent an e-mail to terra and she was very quick to respond. not only that, but i also received a follow-up phone call to verify the exact part that was missing. speaks volumes about the kind of people we are dealing with, they go that extra step to make sure things go as smoothly as possible with their customers. thanks.