Dueling is for suckers. Any of these guys told you about running out your ammo to gain a weight advantage? And there's other tricks they would tell you about either on these boards. 
All of that is seriously overblown, yes you can gain a minuscule edge but its mostly in your mind. Duel any of the multiple loadout planes (jug, pony, 190, 38 come to mind) and you'll see that the lighter gun package has a very minimal effect.