If a mob with documented violence says they will show up and then they do, I think lethal self defense is justified, even on a large scale.
I would pick a 12 GA 3-inch mag cylinder choke with the #4 Buck that has about 42 pellets per shell. It may not be the most lethal shot size, but it would pay back the maximum number of communists.
There is a charming firearm called a “street sweeper”; it is a 12 gauge shotgun with a 30 round drum magazine; if I remember correctly the ammo is 00 buckshot.
One of these with some extra magazines laying about would do the job of self defense nicely — and send a very painful and lethal message.