In brief... none.
They are one of the very loose or casual use of the terms in the Period... akin to "rifle" when it was a musket... or "musket" when it was a rifle-musket"....or "rifled-musket" when it was a rifle-musket.
But, in general...musketoon seems to be an older usage.
Part of the problem comes out of the old British tradition where the difference was not based on length, but rather whether it was "musket bore" of .75 or "carbine bore" of .65.
Still being really brief here...
The U.S. made a shift between musketoon and carbine with the Model 1847 Musketoon series which were .69 smoothbore. Next was the Model 1855 Rifled Carbine and M1855 Pistol-Carbine in the new .58 caliber.
Last edited by Curt-Heinrich Schmidt; 03-07-2017 at 01:25 PM.
In gleichem Schritt und Tritt, Curt Schmidt
Not a real Civil War reenactor, I only portray one on boards and fora.
I do not portray a Civil War soldier, I merely interpret one.