Since I couldn't remove the outer barrel, I disassembled the hop chamber inside the receiver, used a screwdriver to push the clip and it snapped
@Adolf Hamster yeah. Oh, now the motor vibrates like crazy -.- must have fucked up something when reassembling the thing -.-
No, I just unscrewed the cage to open the box, then reassembled it. the motor has some lateral play (spins on its axle by 5/10 degrees when operating) I'll try to sort it tonight when I get home. Thank god it's a V3 so all it takes is one screw on the grip to uncover the thing.