It seems obvious to me that some heavy projectiles, North and South, were coated with a soft metal to limit their tendency to richochet off the sides of armored gunboats. I suspect the idea originated in Europe, probably England, where extensive testing was being done with rifled ammunition and armor. Anyway, it is important to note that the South did quite a bit of coating their big projectiles during late 1861 thru mid-1862. Maybe the practice continued afterwards but I haven't seen the proof. To be more specific, the big Rebel guns defending the Mississippi River were issued many copper coated (and a small number coated with "white metal") as you will see described on the invoices below. All was done by Quinby & Robinson, a great Memphis foundry that called itself "the Tredegar of the west."
The first entry on the first item says: "October 30, 1861 - Covering 108 Archer shot with copper." Look at the fourth entry on the first item, "Covering 2 James 32 pdr. shot with white metal." And second from the last on the first invoice below, "Covering 200 Archers with copper." All of the other invoices, below, report making copper-covered big projectiles including a few Reads. The Archers they were making were the style Jack Bell pictures on pgs. 188 & 119. Jack should note that they were cast as 24, 32 and 42 pounders. It was one of several regulation patterns for the CS army and navy during the second half of 1861. As of today, only a few 32 pdrs. have been found around Island #10 - none of those were copper covered. Many of these big Archer shot in 32pdr. caliber were made by Tredegar during the same period with no mention of copper coating.
There are other interesting facts about CS projectile production found in the contemporary invoices below. Look at the eighth line on the first page below. It reports the manufacture of "54 9pdr. James Rifled Shot Turned." So, Quinby & Robinson were also making quantities of 3 inch James shot. These have probably been dug at Shiloh. Previously, I thought all were made in New Orleans by Leeds who manufactured a couple of thousand in 3 inch and 3.3 inch caliber. Another interesting item around the middle of the first page below is "Boring out one old cannon." This was an old iron 4 pounder reamed and rifle to a 3.35 inch caliber. Tredegar bored out 50 of the state's (VA) old guns to 3.35 caliber during late 1861. In early 1862, Col. Wright, ordnance chief in Tennessee, requested Tredegar send 200 of their 3.35 Archers to him - that is the amount required to be carried by a single gun in the field.
Read these pages carefully. This was a transitional period in Southern ordnance production and their is much to learn. When Memphis fell, Q & R moved as much as they could save to Columbus, Miss., and later to Selma and Georgia.