At one time or another most forum members have experienced the same problem. Never saw an explanation.
Looking at the data the 9mm only gets good marks with +p+. Those are pretty snappy rounds in a small poly gun. I wonder which models are rated for +p+ or are they all at this point? If I had no other considerations beside stopping power I’d go with a 357 Sig. But that’s not the case.
The fact is I can’t afford thousands of the best bullets for every caliber in the house so if push comes to shove someone could endup getting shot with hard cast wadcutters. They tend to make 2 holes.