BACK UP YOUR FILES THAT YOU ARE REPLACING!!!

1. OpenIV
2. Go to GTA V/x64/audio/sfx/WEAPONS_PLAYER.rpf/
3. Edit mode click yes click on new tab - Import OpenFormats - add the file ptl_50cal.oac click ok
4. Go to GTA V/x64/audio/sfx/WEAPONS_PLAYER.rpf/Resident.rpf/ 
5. Edit mode click yes click on new tab - Import OpenFormats - add the file weapons.oac click ok
6. Enjoy