I have an airsoft replica of an XM177, and it's pretty close to the real thing. It's a great deal of fun and is worth more now than when I bought it.
It's quite handy for evicting unwanted squirrels and cats from the area without doing any harm to them. The fact that's full auto and the mag holds a hundred airsoft BB's is pretty cool, too.
Unfortunately, the internal gas tank is only good for about a hundred shots, too, so reloading is a bit of a chore. My solution is to get a small tank and regulator and stuff that in the backpack and feed gas to it via the provided external gas port. You can go all day on that, practically. Any non flammable gas will do and 140 PSI is about as high as you'd ever want to go.
In case you're wondering, the magazine contains a flexible piece of plastic tubing which contains the BB's. They're fed by air pressure directed through the tube from the back to the loading port. You could easily rig up a truly huge drum magazine by putting a few dozen feet of tubing into a gutted or fake drum mag, so long as you provide an air connection both ends of the tube.
The Japanese LOVE guns. I'm quite amazed that their love of guns hasn't led to their being legalized.
I think it's funny as hell, though, that they can dump so much money on an airsoft rifle that looks so awesome, has real optics suitable for genuine sniper duty, and the effective aimed range of the airsoft rifle is about fifty FEET.
CJ