I bought my son, nephew and myself each a HiPoint 9mm carbine for fun shooting, and in the booklet that comes with them, this is one of the accessories they offer. We have AR-15s and want these on the HiPoints for asthetics only, (rifle hasta look mean) but the HiPoint salesgirl said they are not threaded and are friction fit and attached with a set screw. Did some googling, but not much help, so to the experts here. I'm new to shooting and I've never heard of "friction fit" and this set screw deal sounds dangerous. Also don't know what a gunsmith would charge for threading the barrel if I went with a threaded one, especially spending extra $$$ on an inexpensive rifle.