1 Those who did not use them & relied on the sword
British cavalry being the classic example of this, with Marlborough order that his horse to be issued with only three rounds of ball to reinforce this.
2 Those who used them on the charge or prior to a counter charge
French cavalry did this unleashing a volley at the trot before accelerating to a gallop & going in with the sword, though French tactics with horse where in flux & they at versus other times used both the other tactics. Bavarians where also supposed to have on occasion at least fired just before launching into a counter charge.
3 Those for who the Pistol was used as primary weapon
This is the classic Retier style of using them & it was still used by the Austrians amongst others where horse would be involved in a fire fight as mounted shot possibly without charging or advancing to contact
I also concluded that pistols if loaded in a mellee they might have been used opportunistically but could find no evedence any one trained to do that so I am happy to presume its inclusion in the normal mechanics for fisticufs.
So I am left with perennial question how do I model that?
I reasoned that if 1& 2 only existed then I would be best to model pistol use as either a mellee weapon or as the use of fire arms is modelled for foot as a penalty for being unloaded. The problem with this was that cavalry with sword only as its primary weapon was seen with the exception of the French as being the "best" of the three broad tactics but I could work round that. However with case 3 existing with the horse standing off and exchanging volleys with the enemy I could not & I felt I needed to give pistols a range even if a rather short one. it also will allow me to model Horse which fail to make contact due to being "put off by pike or bayonet" firing a ragged volley form the point the charge stalls.
However thank you for the feed back it helps & makes me think back trough my reasoning