This wasn't too long after all the high visibility crime of the 20s with motorized bandits coming into towns to rob banks and such. Cops also had shotguns, rifles, and submachineguns. Sometimes they even had automatic rifles like Colt monitors, which was a BAR variant marketed to piggers.
PIGGERS can't fight an organized group of determined men, only isolated slaves
Think about that - would you exchange being the 51st guy on that side for a team 4x the size but green as hell?