Keith,
Checked further and I find there was a spherical shell projectile for both the 6 pounder field gun and the 12 pounder field howitzer. The 6 pounder shell was 3.58" in diameter to fit the 3.67" bore. The 12 pounder shell projectile was 4.52" in diameter to fit the bore of 4.62" Both used a Borman fuse and possibly other types. I thought that Gen. James rifled some 6 pounder field guns and designed a shell of the James system of rifling to be used in this gun. Can't find mention of a 3.67" James shell projectile but there is a 3.8" James shell used in Type II James rifled field guns.
I still feel that the use of a shell in a 6 pounder field gun was not a commom event because of the limited range and the problem of setting the fuse. The 12 pounder field howitzer had a range of 1,072 yards at 5 degrees of elevation using a shell projectile. I wonder what others think about this?
Ron