The M1911 is described as:

A longtime favorite, this is THE shooter’s pistol.

You can find it in south-east Ocoro province, at a farm in the middle of nowhere. There are a couple of cartel hostiles on the other side of the farm. The weapons case is inside a barn to the south side of the farm.

This location is accessible only over a huge field full of cows. I recommend taking a helicopter, and you can completely ignore the enemies, as they’re not close enough to see you.

I’d say this is an all round pistol with good damage. Unfortunately other pistols certainly have better stats, and one of the main things letting the M1911 down is its 8 round standard magazine. The extended magazine doesn’t do much better at only 15 rounds (found in Koani), sadly this relic – sorry, classic – has been superceded by more modern designs, such as my personal favourite handgun, the 5.7 USG (also in Ocoro).