[Al Skierkiewicz]

I like the drilling holes idea but it takes away from the asthetic value of the the ammo can. You can add fins (painted to match) to the outside of the can so that airflow will cool the exterior, then mount the electronics (the hot bits) on the interior of the can.
Some kind of scoop intake on the bottom would be out of sight and vent holes on the top would allow convection cooling to remove some of the internal heat as well.