A 12 gauge shotgun is an extremely versatile and effective weapon. It offers a variety of loads that can be shot for various purposes. It can shoot fine pellets to kill small game and birds, or large pellets to take down large predators (or for combat), as well as slugs for hunting large game. Interchangeable barrels increase the options available to you. 12ga shotgun ammo is plentiful and would be easy to find during SHTF. Truly you cannot go wrong by keeping a shotgun for SHTF.
I haven't noticed any short supply of any shotgun ammo.Considering the ammo distribuion the last 12 months in North America, with factories running wide open, if you don't already have the ammo, you're not going to get more during a SHTF afternnon.