Hi John,
Quoting the 1862 U. S. Ordnance Manual, pgs. 276-7 "For the greater security of field ammunition, the cartridges were covered with paper cylinders and caps . . . The caps for shells are stained black, for spherical case shot, red; for shot, not colored". I believe the words "greater security" referred to protecting the powder bag from an errant spark. Incidentally, I have seen remnants of the cylinder still remaining under the twine in about four examples not of shot, none were colored. If that is generally true, I would like to know how they could determine a shell from a case from a shot when the cartridge was stuck ball down in a limber ammunition box except for their position in the box. Regards - Bob Gregory