While conducting family history research in East Tennessee, I've come across some references regarding rifles. When talking about the rifles that men picked up to protect their home and go to War ca. 1812 onward, the term squirrel rifle is used to describe them. I would assume 40 and smaller with the 36's, 38's and smaller in there.
"Rhea and Meigs counties(Tennessee) were set-
tled by the same people, coming from Southwest
Virginia and upper East Tennessee in carts and
flatboats, and from North Carolina on foot, bring-
ing their possessions on pack horses. They were
largely of Scotch-Irish descent. The first settlers of
these counties had followed Campbell and Sevier at
King's Mountain, and Jackson at New Orleans.
Their descendants were with Jessup in the Glades
of Florida, and with Scott in Mexico. They were
men who were ready to shoulder their squirrel rifles
and face an enemy, whether he wore the red coat of
a British soldier, the war paint of a savage, or car-
ried the lance of a Mexican." VC Allen, Rhea and Meigs County in Confederate War