I'd have to agree with Ron that this (hub to hub) would be a configuration dictated by the lay of the land. I have a great first hand account from the 3rd Co. Richmond Howitzers concerning the burning of Pole Green Church. They were of course credited with firing one of the first "free worship" structures in America. According to Sgt. William S. White's (gunner on gun number 4, a 12 pounder Napoleon) personal recollection, his gun was almost 300 yards to the left of gun number 3 "in battery" as the Confederate's made their way out of the Tottopotomy Creek bottom preceeding the battle of Cold Harbor. 300 yards. But if you visit that area you can understand why the spread of guns in the battery. At Malvern Hill there were supposed to be 29 Federal guns firing on the ridge "hub to hub". I don't know the exact length of the gun line, but judging from the lay of the land they would have had to be massed together pretty close. That's one of my favorite "meditation" spots, and only about 10 miles from my house. There were reports that the artillery on Malvern Hill could be heard in Staunton, Virginia.