Ammo... start reloading and find what works, I reload 45's and with stock DA/SA HK45's can do decent 25 yard slow fire groups.
25 rounds in a row on a B8 Target with the Full size HK 45 and 25 out of 26 with the compact is to date my best effort.
I am also Obsessed with accuracy have done 25 in a row with my stock DA/SA P30l but with factory ball ammo groups not as tight.
Stock HK 45 (25) yards 10 rounds 3" group
Nosler 185 Grain Bullets
5.4 Grains Tight Group Powder
Starline brass
Try some of this stuff if you don't want to reload http://store.asym-ammo.com/9mm_s/94.htm