Guns are funny beasts. What shoots great in one won't shoot very well in another.
I just got an M&P 2.0 9MM, 4&1/4" barrel and the PC (Performance Center) model. I went to the range yesterday and shot some ammo I was hoping would group well in it. Those reloads turned my 1.0 9MM 5" PC gun into a pretty nice group shooting pistol. Kept me from opening the safe door and setting it on a shelf. Darn. Winchester 115 grain FMJ (the white box stuff) is close, if not slightly better shooting in the new pistol than my reloads. That gun "likes" something else.
When you get a good load, don't stop. Keep experimenting with bullets, powder, etc. and find back ups for your good shooting load so you'll be ready when your favorite powder or bullet isn't available.