I agree with the posters above who suggest the JHP bullet is longer and would tend to increase velocity(all else being equal). Powders like 2400 and Accurate #9 perform best with full case loads. Reduced loads don't fully burn and leave powder granules. I experienced the same thing 20+ years ago.

I'll share another lesson I got shooting 9mm handloads using mixed brass. I was getting 4 to 6" groups at 15 yds. off bags with my Beretta M9. I got much better groups using only one brand of brass....doesn't matter what brand as long as they are the same. Try it...doesn't cost you.

Have fun.

__________________
Bob.
SWCA 1821