John,

I'm not convinced that Whitworths are excluded from this simply because he didn't state which type of breech loader. On the other hand, I think they can be excluded for pragmatic reasons. Breech-loading Whitworths were about 20" longer than 12 pdr Armstrongs and about 200 pounds heavier, making them unwieldy choices for Loring's canoe scheme.

That leaves the Clay and Armstrong breech-loaders as best I can tell. The 6 pdr Armstrong (2.5") was only about 60" long and weighed 336 lbs. The 12 pdr Armstrong (3") was 83" OAL, and the tube weighed 918 lbs. I've not found much data on the Clay (no survivors) other than it was 3". E.P. Alexander complained that its shots all tumbled and that the breech cracked after firing seven rounds.

Loring was a disaster for the CSA at Champion Hill. Arrogant and insubordinate, he was one of the problem children of the CSA.