yep, blue white box, auto 9 c got mine from redwolfairsoft.com outta HK.
yes, the back half has plenty of weight to it, and front is light, i have took mine down to have a looksee, and i have seen what you said. i thought of doing the same, but for what i want, i think it will be just fine as is. i also got a m93rII and it had a torn chamber seal, so i had to order a replacement from kwausa.com. its a kwa m93rII.
that gun i will use the most. one thing i was disapointed in, i thought i would be able to use the mag from the 93r in the robo gun. but it wont work. the reason is the air seal on the mag is forward more from the robo's mag. other than that, their the same, it fits and all, but mag seal wont match up. i ended up gettin a extra mag tho, so i got 2 that work on the robo gun.
that 3 round burst is just freakin cool. its powerful enough, that at 10 feet away from a metal trash can, it puts dents in it from the bb's hittin it. i mean definate discernable dents .
i was plinkin my mailbox from a 100 feet away and it was plinkin it pretty good. so the robo gun has got alot of power to it on green gas for sure.
redwolf has got a upgrade barrel i plan on gettin soon as its in stock. a nine ball brand.