"Well, these two are ballistic, this one's radiation and that's energy," he said, leaning forward and pointing to each weapon in turn. Did radiation exist wherever Percy was from? He didn't know. It really didn't seem all that common here. Not like he had a geiger counter or anything, but by now he sure as shit knew what taking rads felt like.

"Do they have atomic energy where you're from?" Maybe when he was from. MacCready didn't know when the gun had been invented in the first place. Maybe that was what they looked like in the beginning? Hell if he knew. History from any time before the bombs dropped wasn't really all that detailed.