I found the original account
here (search for "Tarleton").
There were many Englishmen who had seen service in America and learnt what a formidable weapon in the hands of a skilled shot a rifle could be. Colonel Hanger, who was one of them, relates an instance bearing on the point. Writing in 1814, having served during the war as a captain in the Hessian Jager Corps, he says that he never in his life saw better rifles, or rifles better used, than those made in America, and adds that they were chiefly made in Lancaster, and two or three neighbouring towns in that vicinity, in Pennsylvania. Their barrels, he says, weighed about 6 lbs. 2 or 3 oz., and carried a ball not larger that 36 to the pound. This is equivalent to a diameter of a little more than half an inch, a smaller calibre than was used in the military arms of this country until the adoption of the Martini-Henry rifle. Yet Colonel Hanger says that he never saw in America a rifle of larger calibre than has just been mentioned, although he had seen many hundreds. He gives the following account of an incident in the war, showing that the use of the rifle at a distance of 400 yards was unusual in those days, and taken to be a very important developement in war : ”” * Colonel, now General Tarleton, and myself, were standing a few yards out of a wood, observing the situation of a part of the enemy which we intended to attack. There was a rivulet in the enemy's front, and a mill on it, to which we stood directly with our horse.s' heads fronting, observing their motions. It was an absolutely plain field between us and the mill ; not so much as a single bush on it. Our orderly-bugler stood behind us about three yards, but with his horse's side to our horses' tails. A rifleman passed over the mill-dam, evidently observing two officers, and laid himself down on his belly ; for in such positions, they always lie, to take a good shot at a long distance. He took a deliberate and cool shot at my friend, at me, and the bugle-horn man. Now observe how well this fellow shot. It was in the month of August, and not a breath of wind was stirring. Colonel Tarleton's horse and mine, I am certain, were not anything like two feet apart ; for we were in close consultation, how we should attack with our troops, which laid 300 yards in the wood, and could not be perceived by the enemy. A rifle-ball passed between him and me ; looking directly to the mill I evidently observed the flash of the powder. I directly said to my friend, * I think we had better move, or we shall have two or three of these gentlemen, shortly, amusing themselves at our expence.' The words were hardly out of my mouth when the bugle-horn man behind us, and directly central, jumped off his horse and said, ' Sir, my horse is shot.' The horse staggered, fell down, and died. He was shot directly behind the fore-leg, near to the heart ”” at least, where the great blood vessels lie, which lead to the heart. Now, speaking of this rifleman's shooting, nothing could be better; but, from the climate, he had much in his favour. First, at that time of the year, there was not one breath of wind ; secondly, the atmosphere is so much clearer than ours, that he can take a more perfect aim.' ' I have passed,' he adds, * several times over this ground, and ever observed it with the greatest attention ; and I can positively assert that the distance he fired from, at us, was full four hundred yards.'
Regards,
Joel
