Shotgunner question

When i first started the game my very first ever character was a shotgunner and i loved it. I then discovered heavy weapons and archery and never looked back at shotguns. Now with the introduction of the 4 star fracturers mod i have been having an itch to creat and run a new shotgunner character. I know the cold shoulder is the king of shotguns but i also know it's not modable. So my question to you all is which is the current best shotgun in the game that can be modded ( by best i mean damage and utility) im guessing it's the combat shotgun but that seems kinda weak. Yes i also know shotguns got nerfd so im also gonna try to treat it as a challenge run too