Well, I guess any advanced weapon would need fuel/ammo? Let's guess MC found the machinegun, how he would rearm it?
So best bet is "personal connections":
let's say you've decided that the world around you isn't good enough and needs correction. You take a big club and then go somewhere. You find someone there and directly lay out your doctrine of the struggle for a better world. If he doesn't agree, you hit him over the head with a club - one opponent less. If he agrees, he also takes a club and moves with you, asking similar questions to passers-by. The winners are those who are more numerous. They declare themselves true fighters for peace, and the others - bright victims who fell for a wonderful future. (c) Belianin.