I agree with either the 9mm or .45acp over the .40.
9mm as stated is cheaper if you buy factory, and you get higher capacity. For defense, 9mm bullets have come a long way for good stopping power.
Now on to the .40. I reload for all of my guns, and the pressure in the .40 is close to the .45acp while shooting a much lighter bullet.
I have a good example. I own both a Beretta 8040 Cougar and a Beretta 8045 Cougar.
Both guns feel the same for recoil, and the only advantage to the .40 is two extra rounds in the magazine.
Everybody likes something different, but I'll take a 9mm or .45acp any day to a .40
NRA Chief Range Safety Officer
NRA Pistol Instructor
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DNR Certified Firearms Safety Instructor 37 yrs