Remember that these are stout loads in an AR. When I started into this I had issues with ejecting a loaded round without leaving the boolit in the throat. I started with SDs over 100 fps and tightened the crimp until the SDs got down under 30, and I could eject a loaded round. Groups followed suit. This was well before anyone made a "factory crimp die" for the .450B. The Hornady seat/crimp die wouldn't begin to hold a 300 grain boolit in the case if you let the bolt release chamber the round. That "waist crimp" made the difference between 5" groups and 2" groups. The boolit I designed on the left in the picture was pretty frustrating. I shot many, many 5 shots groups with three touching and two off to the side opening the group up to 2-1/2 or 3". At the time I thought the gas port was disrupting the check, but over time I've come to think that maybe it was just too much lube.