A (probably stupid) gun idea I had
 

Image: https://i.ibb.co/rs3M6FQ/Derrinbine45410.jpg (I made it under 10 minutes just to illustrate the concept. Don't think too hard about it.)
Type: Four-barreled derringer/carbine hybrid with a 16'' barrel and a retractable stock
Caliber: .45 Long Colt / .410 bore
Possible uses: Self defense and pest control

The image is an amalgamation of a Signal 9 Reliant, a S&W Model 320 (forearm) and an MP7 (stock).
I'd like to hear opinions. Is it an interesting design, or is it cursed and shouldn't exist?

The derringer layout and the long barrels seem to be working at cross-purposes to each other. Barrels have weight, and multiplying the number of barrels increases total weight quickly unless the barrels are (very) short and/or (very) thin. The derringer layout also means the point of impact changes noticeably with every trigger pull, especially if used at mid- to long-range (which I assume the 16" long barrels are intended to be used for, coupled with the implied longer sight radius). Reloading quickly is also going to be an issue unless moon (actually square) clips are available and buying them is going to be an extra expense, not to mention the time and effort you need to load and unload ammunition onto or off of the clips.

For pest control from the barrel of a gun, I assume most people would rather spring for a pump-action shotgun in .410 bore, or even a snubnosed revolver in .410 bore and load it with ratshot.

Did you get this idea after playing Metro: Last Light and seeing its "Quadlet" four-barrelled shotgun in action?