Just ran another 30-40 rounds through mine today. I built up the rear top of the mag with some aluminum foil tape to take away some of the fore and aft rocking of the mag. It definitely helped but, its a temporary bandaid solution, at best. Looking at it some more, the feed ramps are pretty steep and very roughly cut, about what you’d expect for a $400 rifle. Maybe cleaning them up and polishing them some would help. Kind of hit or miss with which bullets feed better than others.
FWIW, I’m having the same feeding problems with my RAP 243 as well. Even with the AICS “style” single stack mags. It’s not as frequent as the Grendel but, some bullets just don’t want to feed and plowing nose first right into feed ramp and jamming up, and the harder you push, the more they don’t budge. Very irritating. To the point I actually broke the stock on the 243 today doing battle with it, so, got another Magpul from “Buds” this afternoon.
FWIW, I’m having the same feeding problems with my RAP 243 as well. Even with the AICS “style” single stack mags. It’s not as frequent as the Grendel but, some bullets just don’t want to feed and plowing nose first right into feed ramp and jamming up, and the harder you push, the more they don’t budge. Very irritating. To the point I actually broke the stock on the 243 today doing battle with it, so, got another Magpul from “Buds” this afternoon.