Last year, I acquired a really nice specimen of the chamber used in the Agar “coffee grinder” rapid fire gun used in the Civil War era.
OAL is 2.875" +/-
A long time advanced collector of such material asked to see it to compare to the specimens in his hands. There is an even more rare variation used in the earliest Gatling, somewhat shorter than the standard Agar chambers which he has.
We were both surprised to discover mine is actually LONGER than his by 1/8" . . . .
In Vol. III of his seminal series on Civil War era cartridges (at p. 277), Dean Thomas shows the Gatling round, noting its OAL as 2.75" and the text discussing the Gatling system references the Agar design as being 1/8" longer, which would be consistent with my example being for the Agar. Yet in Lewis, p. 229, reference is made to specimen 271 - ‘0.58 Union Machine Gun’ with a note in the far column of ’ “Coffee Mill” gun ’ . . . which was / is the nickname for the Agar system, and here, too, the length is cited as 2.75" . . . so if the Agar is indeed longer than the Gatling, this makes my 2.875" item the “XL” of the party.
Edit / additional information follows:
Although he didn’t cite the material, the fellow with the shorter cartridge did determine that the Agar was in fact 2 7/8" OAL, making the shorter round he has the Gatling. Why Lewis refers to it as ’ “Coffee Mill” gun ’ is a question remaining to be answered, but I’ve been informed this was originally in his collection, so it would seem it simply wasn’t included for whatever reason.
Thanks to all for their help and suggestions!