It's just my opinion but if you're going to put a non-magical character class in my fantasy game, then by golly, it should be realistic. If it's magic, then it's magic, but if it's not magic, then it needs to adhere to some sense of realism. Sorry, Charlie! No gunslingers in my campaign!
I, too, have read the Sharpe's novels by Cromwell. Excellent reading! That's as fast as it gets for non-magic firearms!