MGs are fine.
Silencers are fine.
As others have said, handguns are now an AW if they have a threaded bbl.
I have threaded bbls for my Glock 17, 19, and 34. I plan to register all of them as AWs. My goal is to bump my number of AWs up as high as I can.
Just as an exercise. I figure I can get close to 100 if I work things right. Remember, that "any part that can be used to convert a firearm to an assault weapon, is an assault weapon". (I'm paraphrasing). So by that logic, the barrel can be considered to be an AW. (Unless its purchased as a replacement part for an already registered AW. This is settled law as its been adjudicated with machine gun spare parts.)
But by that logic, every threaded bbl, every AR mag release button (could be used to convert a fixed mag rifle to a detachable mag rifle), every flash hider, every pistol grip, is an AW. ALL OF THESE ITEMS ARE AWs, in and of themselves.
So even if you don't intend to register your ARs. Register grips, and all that crap. Burry them in data.
With respect to .22s. The exemption given to rimfire is only in the rifle portion of the law. So a .22 pistol with a threaded bbl is an AW.
Oh shoot. I just realized that my 22/45 Lite has a threaded bbl and is now an AW. Ha. I better spend the next few months thinking of this pretty hard because I don't want to miss anything.
Here's an other interesting thought. I have a threaded bbl for my G19 because its a great suppressor gun. Not as muzzle heavy as a 17 or 34. But its also one of my main carry guns. If I register it as an AW, I can no longer carry it because as an AW it must be transported unloaded.
****ing ridiculous.