Shotguns

This is the tree of the shotguns, it goes from the least good weapon to the best weapon of the category.

Driller
It's a double barrier shotgun, its sight allows it to play both in mid ranges, but even on really long ones. It's recommended not to use this up close and personal, but more like a sniper, this because it has a really limited ammo capacity, and for the aim down sight (and rifle shot) secondary.

Shotgun
It's your classic pump action shotgun! It's best to use it up close and personal, even more with its secondary, because it gives you a double shot. It has only 8 rounds and you need to reload each shell

Concussion Gun
It's a sci-fi pocket shotgun, its burst wave can help stunning and repulse away hordes of enemies. Unfortunately it has only 2 rounds per mag, it is not effective on long ranges and it has no secondary fire. Its best use is to use it as a secondary to stun enemies and run away

FSFS
It's a quadruple barrel shotgun, packing an hit so big that is capable of one-hit killing even the Brutes. Unfortunately it has no secondary fire, and after every shot it needs to be reloaded. So while it can compete even with the BHG, it's not too good in follow-up shots, and if you miss a shot, you are in quite some troubles

Riot
It's an automatic shotgun, with a big magazine. It is way more forgiving than the other shotguns in terms of missing shots, since you can almost instantly follow up shot. Its secondary helps at longer ranges, but watch out, do not overdo, it's still a shotgun after all