Sorry it took me so long to reply,Iwas out of town for the Gateway dynamite shoot which was a blast by the way! The reason I am using mag primers is the fact that they have a harder cup than most and let's face the fact that many post model 70 winchester's have large fireing pins with sloppy hole tolerances. This problem was since remedied by Gre-tan custom rifles.Greg did a beautiful job on my bolt. The load with mag primers performs well and I have a lot of them.The last group I shot with my 6.5-06 measured 9"at 1125yds.Hope this helps and answers your question! Dave