10-07-2011, 02:45 AM
There was a time when they were making carriers with a slightly larger diameter to the raceways, to fit the BCG tighter and more concentric with the bore. Several customers had problems with reliability due to increased friction in the receiver. My understanding is that they had to go back to a standard diameter, but I haven't heard that from the horse's mouth. I've ordered slickside chrome bolt carriers from them for retro projects, and they are fine. I would just use an M16 carrier with the Grendel.