Well R4 MP7
I have one, ( and a dead one too )
the first one, the one that is now dead was decent as hell, shot a good 60-70 foot. But, the gearbox got striped wile changeing fire modes wile fireing. ( never loan a gun you arent willing to risk having it break )
the second one i got, came from airsplat, was like 76 bucks, and arived with 2 missing frame bolts. In addition to that, this second one i got shoots crappy, I think the hop is messed, but i havent bothered to take it apart to find out.
Overall, the gun feels and sounds great, but as far as how good a gun, Dont buy it if you cant afford to buy it as a novelty, I dont think it is woods field worthey.. However,, In close quarters, where range dont matter so much, it would definitley be a contender.
Sidenote, the battery for this weapon is a specialty battery, and isnt very big mah wize, I think its like 6-800 range. but the key thing to remember is its is a specialty battery, you just can put any old battery on it unless you go external.