Ya, in the Single Action days you had to line up each cylinder bore with the loading gate. Flutes let you do so by touch, in the dark, or at speed in any light.
In fact, I think a lot of the even earlier percussion guns were unfluted...Colt Patterson, Dragoons, 1851/1861 and such I seem to recall were unfluted? If so it wasn't until the need to stuff metallic cartridges in the rear that fluting became more popular, and necessary. (I'd go google pics of percussion pieces but I've been typing all night and gotta catch at least a couple hours...if I'm wrong, somebody will chime in shortly
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