[mikaelluioy]

actually they can make batteries that last for years..as far as zach question.. they can embed it inside the butt in a way you would have to saw it in half to find it..

That depends on the load.. And the stock is about the only place left to hide such a device..

Weapons get disassembled and cleaned all the time. It would have to be concealed just about perfectly.

And, absent such a device.. How would you expect to "track" them?