As long as they're in your checked bag there shouldn't be any problem.
You could even have them loaded.
(Technically, you could have them unloaded in your carryon, but I'm pretty sure some TSA drone would give you grief 'cause they don't really know the law.)
Here's a blog post I did about the federal law for flying commercial w/ firearms.
Use the link in the second post to read the actual law.
IIRC, the only thing it says about magazines is included in the part about ammunition - if the magazine is loaded, it has to be in something so the primer is protected. (Apparently whoever wrote the law thinks that something could bump the primer & the cartridge would fire inside someone's luggage.)