1.) 9mm
2.) 45 acp
3.) 357 sig
4.) 40
The first pistol I ever bought was a 9mm, and through practice have become very efficient with a 9mm, and I still carry my M&P 9c almost every day. I also shoot 357 sig naturally well, and 45 acp pretty well, hopefully with more practice with my new kimber and I will improve even more with 45. I don't shoot .40 that bad, but definitely shoot it the worse of these calibers.