Yes, i read that before as a reason for smooth bores for dueling. English also frowned on distinct sights, finding "taking an aim" to be un-gentlemanly. it was the ritual that counted, most duels ended without a hit, firing the shot was good enough.\
However, in sections of the US with heavy French or German influence, the English rules were often ignored. "Scratch" rifling, usually hidden by a very long counterbore type crown, certainly was used. But remember, the pistols were loaded by the seconds, and they'd probably detect it... plus the injured party was given his choice of the loaded pair, so they both were rifled (just that one shooter didn't know it).
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I did have to replace one screw, and got a lesson in doing so. Were made with all screw slots ending up pointing along the long axis of the bore when fully tight. To replace the screw, had to find a slotless screw (thick head)...cut a temp. slot in the crew... lathe the head siameter to the right size... screw it in tight...make the long axis on the screw head...cut a slot along that mark... lathe/polish the hed down to remove the temp. slot... then ended up with a new screw that was pointing the right direction.
Know 98% of that was just for show, but i will say that having all the screws line up in the same direction certainly does let you know when something is coming loose.