I am in need of an AR57 Auto BCG. For those who don't know what an AR57 is, it is an AR platform rifle chambered in 5.7x28 that uses PS90 magazines. It ejects the spent brass down where an AR-15 magazine would be (people modify AR magazines to catch the spent brass). Most of the rifles shipped with the semi auto BCG. If anyone has one of these they want to part with, or know where I can find one, let me know. Thanks.