How to add:
To add the guns you will need IVTweaker
1. Install IVTweaker if not installed
2. Make sure that in "IVTweaker.ini" you set "MaxWeapons=" to 100 or above and "MaxWeaponModels=" to 200 or above
2. drop everything in "Beretta handguns" into: Game directory>modloader
3. to make sure handguns have sounds, use RAGE audio toolkit to open "game.dat16" and duplicate any gun sound (preferably pistol) and rename them to "W_SAMURI" and "W_CUTLASS" (with the TACE Mod, I prefer CZ75 sounds)

How to obtain:
There are a few ways to obtain addon weapons which can only with mods. The easiest is with a trainer, especially zolika's trainer. Another way is with a weapon-pool mod for npc's to spawn with. The most fitting is with a mod by LotsofEds which allows addon weapons to be sold with any preference:
https://github.com/LotsofEds/ImprovedGunstoresIV

Once you've chosen your method, you can enjoy these guns! :3