It's a pistol, a heavy one, but it's a pistol.
A PTR PDW rip off, HK91K or something.
In this picture it has a mag lock on, and of course a 5 round hunting mag is usually locked in place.
In a SHTF situation the CA-comp lock and mag are removed and a nice 20 round pre-ban slipped (legally owned) in.
This carries across the back discreetly, and makes so much noise, flame and chaos, you might miss but still be logistically effective.
The ammo is easily scroungable 7.62x51mm NATO or .308 they both work and it's crazy reliable - thrives on grease and dirt.
The sights are big and bright and set up for me to hit what i point at.
The flashlight might help in a pinch, too.