There are a lot of 650 grain 577s reproofed for 750 grain loads. You are now shooting an eleven pound rifle that should weigh 14 pounds. The result is, they kick so hard, they knock your eyes out of focus for about a half a second.
50 rounds of this, and it lowers your IQ by 20 points. I only fired a few rounds, so I'm only slightly stupider.

Dave