EBR's and other "assault weapons" have to be registered.
This isn't true.
Sales of them are controlled, and may be recorded (you can't purchase more than one in 30 days) but you don't have to register handguns or what MD considers "assault weapons"
rolleyes
when you move into the state or any you build while you're there.
SOME "EBRs" (not even all AR-15s) are considered "regulated" firearms which means they have to transfer as a handgun does in MD -- either at an FFL or through the State Police -- and with a 7 (generally more like 14) day waiting period. Then you get "Disapproved" or "Not Disapproved" (there is no "approved"
), and you take them home. They aren't registered with anyone.
(Now Title II Machine Guns are registered with the State Police, (as well as with the BATFE, obviously) but that's a different matter.)
Like most of MD's more onerous laws, the "regulated firearms" rules are a point-of-sale issue. You can buy a non-regulated AR-=15 (anything with a heavy barrel profile similar to the Colt H-BAR) or a Mini-14 with a fixed stock, and take it home and convert it to a "regulated" format without notifying anyone or doing anything at all. In fact, a dealer pal of mine in Annapolis once explained to me that if I wanted to buy a Mini-14 with a folding stock that he had on his shelf, he'd sell me the mini-14 without a stock, and sell me the stock separately, and I could walk outside and put them back together, and no part of our dealing would fall under the "regulated" firearms rules.
Similar thing with standard-capacity magazines. You may not buy, sell, trade, loan, rent, offer to rent, etc. a magazine of greater than 20 rds. However, you can own and use all of them you want. A trip to VA or PA or WV to buy a big pile of 30 rd. AK mags to take home with you breaks no laws.