subdjoe,
Thanks for the link.
Remember the YT vid that you posted of this British ceremonial horse artillery unit demonstrating their well honed skills at an indoor arena, where one of the guns flipped over as the team made a high speed turn. I was looking for some more detailed information on this unit, and came across one of the officers talking about different aspects of the battery. He (Capt. Dominic Ibbs) said that recruits usually started out on "detatchment," which are the riders at the rear of the gun, then moved up to "center," the two middle horses of the team, then to "wheel," the rear two horses of the six horse team, and finally after 6-8 years of experience to "lead driver," the artilleryman that directs the front two horses.