My go-to loadout used to be Spas usp frag (nowflash bangs) exp. focus(now ammo salvage) superlegs light armor(now imp. melee)
But after reading all of this talk about how exp. focus boosts the spas's damage or strength/whatever and noticing the differences between pacing of the game, i swapped out exp. focus for ammo salvage. Honestly, i'm glad i did. also because....
Smawers tend to use explosive focus... which reduces the shotgun's damage. If im in a match where i have to use exp. focus to counter explosives for whatever reason, it doesn't make too much sense to use a weapon that is countered or weakened by explosive focus.
Now, i normally just turn to a stealth arc loadout. That thing works wonders in almost every situation. It works to free you from tight situations, allows you to pick people off, and lets you deal with snipers. Obviously, it has it's disadvantages, but it's still pretty fun.
Too bad damage is a bit tough to use; it could work pretty well for sniping. You could cloak yourself after a few shots to give yourself a chance to aim and slightly recover or scout.
Also, double armor spas.... i never had much luck trying that out. it's just my playstyle, i know, but it feels tough to actually get opportunities to use the shotgun in such a speed based game. Atleast in grab bag with multiple people..