Fire away. They do suggest that you replace the recoil spring at 3K round intervals. I can definitely tell a difference in the strength between my original, and the new one. BTW, I have an E9 also.
Judging by the difference in report and recoil, S&B JHP 115gr is +P (compared to Winchester Silvertips, for example)...yet it isn't labeled as such. Does anyone have data on that round (since it is my standard in Kahr P9)?