OK, then: why do you refuse to cite this wonderful and mysterious "source", oh omniscient and infallible guest?

Yes, there were multiple-barreled flintlock and percussion weapons manufactured in the U.S.(and Europe) in the first half of the 19th Century. Yes, double fowlers/shotguns were fairly common. So were multi-barreled and "pepperbox" type pistols. Yes, officers regularly purchased long arms and side arms to suit their individual fancy- some of quite bizzare design.

And yes, the U.S. govt. undertook to convert many flintlocks to percusion ignition- tho you're a bit confused- I made no comment about this one way otr the other.

No, three barreled combination guns were not "common". No, they were not known as "Paradox Guns". They are incorrectly called that today by some uninformed "collectors" and compilers of "How Much Is Your Antique Gun Worth"-type publications.

PS: Have you ever read any of the books I've cited?

(OK, Amos, OK- so I lied.....)