If every artillery shell weighed 10 pounds and it had to be horse-drawn in caissons or in auxiliary wagons for supplementary ammunition, the logistical problems must've been staggering. Every horse drawing a wagon full of ammunition, kit foodstuffs and all of the necessary accoutrements of an army must be fed and most of the feed for all that large number of horses had to be carted along because the horses would soon exhaust any vegetation within range.
So more horses have to be used to feed the ones bringing the artillery shells and some horses had to be use to feed the ones bringing the feed, and so on.
I have no idea the quantity of artillery used at Gettysburg, for example, but we know that Pickett's charge ran into a devastating artillery barrage. How many shells at 10 pounds each were expended? How many horses were needed?
The logistical problems posed practical problems for the generals. For example, in an almost heartbreaking message Gen. Longstreet whose orders were to suppress the Yankee artillery, sent a urgent message saying, "for God sake" go now because I'm running out of ammunition. The consequences of running out of ammunition contributed to the fact that two out of three who went up in Pickett's charge did not come back.
We know the German soldiers in Russia in the latter part of the war there were often reduced to horsepower, the so-called Russian ponies, for want of petrol or just for want of machines. Those units that were not mechanized Panzer units were horse-drawn for the most part.
Nor really the case. Alexander had ammunation to support Pickets advance. The problem was not enough ammunition, it was the quality of the ammunition. The Confederate artillery was overshooting the Union artillery positions by 300-400 yards. The heavy casualties during Pickett’s Charge were because the Union Artillery had not been heavily damaged by the pre assault bombardment. The overshoot was because the Selma Arsenal case fuses performed differently than the Richmond Arsenal case fuses. The ANV was using Selma fuses because the Richmond fuse factory blew up in April 1863. A couple months after Gettysburg, the Confederate Ordnance Dept
did side by side tests of the two fuses, found out they performed differently, and ordered production standardized.
For the rest of the war the Selma and Richmond case fuses performed pretty much the same.