I own the select fire m16a1 vietnam type battery powered rifle.
It is very accurate. I can put all of the bb's in full auto fire in a hole about the size of a quarter from around 50 feet or so. Real range depends on if you are indoors or outdoors, and if you pay the extra for the heavy bb's.
They shoot 6mm, 25 caliber plastic balls.
They are all made from plastic, but the parts are very real looking, and in some cases act like the real thing. The sights are adjustible sort of. That is, I can change peep sights, and I can dial up or down the front sight.
The hand guards come off, and the trigger guard(?) piece is hinged, for gloves.
The mag release works, mine holds 69 rounds in it. The dust cover will snap shut, and the recoil from pulling the trigger will open it. The charging handle will pull back and spring forward, but it doesn't do anything.
The forward assist will move in too.
There is even a steel bar to pretend there is a gas tube.
For mine, the battery is in the butt where your cleaning kit would go.
They make an AK, mp-5, mp5-sdc, etc... they even have the m16 with the m203 under it.
The battery powered ones are the best in my opinion, no gas to mess with. They use the regular 7.2 volt rc car batteries.
I have taken mine completely apart(as I got mine before they were importing them into the country,) so I even can tell you how the guts work.
It is an aluminum barrel, no rifeling, and there is a motor in the grip, that pulls back a piston that creates the air pressure when it releases.
They make all sorts of hipo parts for them as well. Faster motors, high cap mags, and more powerful pistons. I clocked it on a crono, and remember around 350 to 400 fps.