Originally Posted by apilar
Straight out of the FAQ section:
Examples of things you CANNOT import:
AEG magazines with fake cartridges (i.e. P90, G36, SG 552 mags)
Frames, receivers, and metal bodies
Suppressors and silencers
Prohibited-length outer handgun barrels (i.e. USP Compact, Glock 26)
Hand and 40mm grenades that look real
That's actually old info and should be updated. Mags with fake cartridges are only iffy. It just depends on how the agent feels that day. Suppressors are OK as long as they don't have foam in them (it's just a rube after all) however some do have foam or ballasts in them. As for the outer barrels you should be able to import them but it's also iffy.
As for frames and recievers yes those aren't good to import.