Thanks to a post on the Sharp Practice forum I think I need to add this
Carcarole by horse this is just a variation on the rotational fire drills done by infantry and is becoming obsolete at this period as far as I can tell it was only used by the Austrians on any large scale & that the preferred technique for those cavalries which used firing whilst mounted was a variation on the French pistol volley then charge with sword without reloading.
It does mean that we need to consider the horse Pistol as a mas combat weapon rather than something the odd Blaggardly villain might use on our hero to compensate for his lack of swordsmanship.
Given that the ranges for formed musketry are what they are I would range pistols as carbines but count the firer as being one level of musketry worse than they are for now. I am however considering changing the ranges a bit and using a similar mechanism to reflect loss of accuracy at range.
Thank you Steffano