This mod increases every gun that fires bullets including shotguns damage by 30%.
And it decreases ammo that you can carry.
Backup file is inside as well now.

Installation:
You'll need OpenIV
Using OpenIV go to the Grant theft Auto 5 files
Open update
Fallow by locating update.rpf/common/data/ai/
Then locate weapons.meta and replace it with file inside a winrar named weapons.meta