RPG with best shooting mechanics?

[HeavenShallBurn]

Far as best firearm mechanics, I'd call it a toss up between CP2020 and Twilight 2000. You might want to follow the advice of BlackHammer and up the damage of CP2020 firearms just a bit if you go that route.

 

[greatamericanfolkher]

Aces & Eights has really cool firearm mechanics. And you can use them with a dartboard too.

If I could get through that book in one sitting I would be running that game already! (but that doesn't make he shot clock any less awesome!)