One factor to be aware of when using a magical gun is what hand you hold it in.  If I remember rightly, the left takes energy in and the right throws energy out.  So if you hold a "warded to keep Murphyonic disruption away from it" gun in your right hand, your ability to do evocation (or any magic) could be badly compromised, either by dampening it or making it just go everywhere when you try to use it.  Hold it in your left hand, and maybe you can't draw in the energy you need to do magic at all... or it sucks the energy out of you instead.

Both good limitations on use of a magic gun.

Better to make magic bullets (ho ho) instead... with "explosive runes" (of force, or electric) for when they impact.

But if the gun was used by nonwizards who want to just work around wizards,  right v. left shouldn't be much of an issue.

Apparantly I don't know much at all about Roman History, and don't general care about the lay of the land to have to make it fit.  I didn't really care where it was happening, as long as it was happening.  Terry Goodkind (Sword of Truth novels) said one of the worst things he did for his books was include a map b/c people focus too much on the geography and takes the focus from the story.

Everything's been done somehow, I'm sure, but that doesn't keep inspired author from making it their own and just plain being awesome.  And no, I haven't read it, either.  I just wanted to have my facts straight. 

I tried to attach a pic, but it didn't work.

 "A massive formation that resembles a white river spans the cave's floor. A closer examination reveals that the odd formation is an intricate crust of tiny calcite crystals."

"I think Snowy River is one of the primo places underground in the world and there's still so much left that we haven't discovered. ... We don't even know how big it is," said Jim Goodbar, a cave specialist with the federal Bureau of Land Management."