GTA IV - Battlefield 3 gunshot and reload sounds
6/25/19 update:
The original download didn't have a readme (sorry) and used the WEAPONS.ivaud file which requires more steps to install. I've added a readme and switched the file to resident.rpf, which can be easily installed. Open your GTAIV folder and go to GTAIV > pc > audio > Sfx and replace resident.rpf.