40 Smith & Wesson.

I only have one 9mm. It's cheap enough to shoot and fairly accurate, light but OK as a defensive option in decent sized guns.

I have several 45ACPs. They can be pretty accurate with some loads in the right gun, seem proven enough as a defensive option, but I've never been particularly impressed with the cartridge's inability to provide decent penetration.

The 40, while not the most accurate in most guns, has what the other two lack and brings it's own special qualities to the table. It is no wonder that it's now a top choice for police agencies nationwide.

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