Imo lower attack speed increase on PBB so it doesn’t rely entirely on that for damage, and increase ammo economy if you put talents into it and lucky bullet, and lower the recoil and spread and firing delay, and it’d be a viable ranged weapon.
It would be fun if each variant had its own type of special shells like arbites shotgun - explosive with bleeding for more effective horde clearing, toxic/incendiary against monstrosities and armouir piercing for carapace.
Weapons special actions underused