Sorry, that was an assumption on my part. At any rate, knowing anyone who may have the authority to check "probably" doesn't know the exact rules either, a copy would probably be a good idea.
I've had cops who checked my license and sent me on my way without looking at Form 4s and I've had cops who still didn't know quite what they were dealing with even after seeing Form 4s. But in most cases some kind of official looking paperwork made them a lot calmer when dealing with a guy who actually has a machine gun.

