i was working up 270 loads once upon a time and had some real problems with unburnt powder, and hence attaining velocity desired. i was using winchester primers. i tried everything, switched powder, tighter crimp, you name it. finally i bought some cci primers and instantly got a clean burn AND desired velocity. primers can make a world of difference. i use cci (given my experience), but that isnt the point. if one brand isnt giving you what you want, try another. it is a variable that needs to be eliminated.