Cap and ball? Oh boy- we had a big discussion on that a while back. I was in the minority as far as carrying those loaded with 6 chambers but there was such an uproar that I decided even on a percussion only load 5 and have the hammer on an empty cylinder.
BUT, just to be a (&*%^&* I'll say that a few percussion revolvers have good pins or deep cuts that OUGHT TO make carrying six okay except if you catch the spur of the hammer on something, etc. In any event, I'll go along with the crowd and say load just five.
They say the average gun fight is at 7 yards, I've had two home invasions and both times there were multiple guys- 2 once and 5 on the second. I'm not sure if a 6th round would make all the difference if the shooting started. Dive for cover.