If you ordered a Mechabox, chances are that it's a mechabox. AFAIK Systema doesn't make Receivers for regular AEG's (they only make PTW receivers IIRC).
Call up CBSA again and ask them to have someone who is *trained* take a look at it. (Assuming that it's a gearbox and not a receiver).
It could also be a fuckup on Redwolf's part though. Maybe you could go in person and appeal it? I mean all it is, is just a set of gears that spin when a motor spins it. It doesn't house anything at all that could remotely be modified to shoot a bullet.
If they seized it based on the invoice comments then they really need to take a look at it not just say it's a receiver.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE