Please back up your files first. I'm not responsible for anything you break.

I've made the install relatively easy, depending on the way you have your game set up. I use the mod folder dectection with GTA Mod Manager

you can either mirror the paths in my .zip 

or

Go to your GTA V root folder (where it's installed)
update\x64\dlcpacks\patchday3ng\dlc.rpf

Open the rpf file with openiv once there open these folders
x64\models\cdimages\weapons.rpf\

Open this last rpf file and enable edit mode in openiv
deag and drp either the 9mm or 45 ACP version

As far as I know you don't need to rebuild, so just close and play.

If for some reason you like my mod and want to use it, go ahead. I don't care about credits or any of that tomfoolery.