Indeed, mods can both subtly and greatly alter the way weapons handle in the game. Brita's Weapon Pack adds a ridiculously large amount of new weapons, attachments, and ammo types across all categories, and others like Abdhaq’s Quick SMGs mod provide an assortment of powerful sub-machine guns. I'd certainly recommend checking out some mods, but make sure you get used to the way the base weapons function first. When you're ready, you can browse on the game's Steam Workshop page. Be sure to check out our dedicated article on the topic, too.