With due respect, it is not "the final word" regarding the use (or not) of "fixed" rifled-artillery projectiles in 1861-1865.
Two days ago, I wrote a lengthy reply in this discussion-thread, then clicked the Post button... and my post failed to appear in the forum. I've not had the time to spare to reconstruct it since then. However, during the long history of discussion of the subject in this forum, I've posted MULTIPLE scans of surviving original civil war Ordnance Receipts of rifled-cannon ammunition issued in the field, which very specifically list the issuance of "fixed" rifled-cannon ammunition.
Newer members may not have been told about the past discussions and posts about the subject. See in particular, past discussion of Tie-ring Base projectiles, and "Those pesky little Xs", and other discussions regarding "fixed" rifled-cannon ammunition.
Older posts aside, I posted a photo of one of the surviving Fixed rifle-shells Ordnance Receipts in this current discussion. It lists:
121 Rounds Hotchkiss Case Shot Fixed
11 Percussion Schenkl
11 Cartridges
As I've said, it is NOT the only such specimen. But apparently, it (and the several others I've posted) are being ignored/dismissed. Those original civil war dated in-the-field Ordnance Receipts and rifled-ammo crates marked "Fixed" are the final word on the subject.
The explanation for lack of space in rifled-cannon ammo crates marked "Fixed" ought to be obvious. We know that packing iron projectiles with LOADED powder-bags in shipping crates is unsafe during shipment. The simple explanation for the Rifled ammo crates marked "Fixed" is that the powder-bags ("cartridges") are indeed affixed to the projectiles by the issuing Arsenal, but the attached bags are unfilled.
An 1866 document which does not show Fixed ammo for rifled cannons may reflect the situation in 1866, but the 1861-dated crates and 1863-1864 Ordnance Receipts speak beyond contradiction for the wartime years.
For the convenience of newer members who have not seen the past posts, here are a couple of the several wartime-dated Ordnance Receipts I've posted showing the issuance of Fixed rifled-cannon projectiles "in the field."
Regards,
Pete