Why what?

I think what you are asking me is why I can't shoot the Premiums in a semi-auto. On the new boxes, its says not to shoot them in a semi-auto. My old boxes, which I used up last year, weren't marked that way. But, it may explain why the primer came out of a couple of casings when I was at the range getting prepared for last deer season. I guess they are loading them a little hot like the Hornady Light Magnums.