Thanks for the info folks! It’s strange though, as I’ve loaded a 150 grain SST with 50 grains at 2.8 COL and the same with the GMX, only difference is that the GMX is a longer bullet so I never had the guts to fire it. When you shake the cartridge near your ear there is no sound whatsoever, so I’m worried that it’s a compressed load. I was following the Lee loading guide too, so in theory it should be fine.