I like to reload my pistol around 10/11 shots to keep with realism anyway. Obviously not everyone does this. With some semi-autos, you're talking about a magazine capacity in the twenties. Keep in mind that you're obviously going to be more careful even under fire with your 6 shots; a player who believes he has 28 in the magazine is more likely to fire blindly.
Whether or not a revolver is a good sidearm is really dependent on how you use it. I use my pistol more than I use my rifle, so I don't think I'd want to be in your situation. If it's truly just a sidearm in your case, I think 6 shots is generally enough. If you can't take 'em down in the time it takes to fire 6 shots from a revolver, you really should have reloaded your primary instead.
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