Morning Iris7.
I just figured load both barrels with grape or canister instead of using a chain.
Agree on the canister or grapeshot. I don't think mass production of Maxim guns would have been possible in the South, although the North could have done it (just barely). Anachronistic as all heck, of course, Maxim developed his weapon during 1881-85.
As far as barbed wire goes, the first mass production started in 1868 (google) just late for the war. Modern barbed wire went into production in 1874. Smooth wire was used successfully in the 1861-65 affair, though, as I recollect.