In simplifying the game design to achieve fast play, I decided against having different factors for rifle-armed skirmishers, but if you think it appropriate for smaller games or where rifles are plentiful, for rifles, one could have 6 and 12 centimetres for short and long ranges, with a -2 at short range against other skirmishers - that is within 4 centimetres.
I intend to test this with the Vimerio scenario - I expect that the rifles should be able to keep their distance from any advancing French skirmishers in broken terrain... well, that is until a formed unit combat occurs.
Mike.