I don't post too much nowadays but I thought I might help u risk losing some money. There are strict laws against automatic weapon magazines (or there were anyway until not to long ago) and anything that looks like one might piss of a customs agent. My uncle has an empty M16 mag which is technically "illegal".
I wouldn't try, even if it sounds like you're ordering one for a GBB. I don't think they'd let the slide slide (master of pun :smack: ) since it looks too real.
I know the temptation man...for anything airsoft from the US. You'll eventually give up and realize you're stuck with these prices.