THIS is what firearms looked like when the 2nd Amendment was written ...

[Spider Jerusalem]

76. Was it a weapon then in common military use? No.

Was it a weapon that could have been conceived as being in common military use given the available technology of the time? Again, no. The common weapons of the colonial era militia were the Kentucky rifle and the Brown Bess musket. The standard issue weapons of the US Army for a long time after this period were single-shot muzzle- and breech-loading muskets, rifled muskets and rifles, from the 1795 Springfield through the 1873 Springfield, only being replaced in the 1890's by the M1892 Krag. Saying that "well here is this impractical and limited-production weapon that fired more rounds and was never in military service, so there!" isn't really any kind of argument that men of the late 18th century could have imagined such weapons as practical for military or militia use.