My first shotgun was a .410 Mossberg 500. Seeing it gave me the idea. By shortening the barrel, and putting on a short synthetic buttstock, I ended up with a trim and nicely balanced gun. And let's face it, the .410 is alot more versatile than the .22 lr, great as it is.
A fellow on another forum ask for pictures, and since I finally got around to taking some, I figured I'd post a couple here.
The first shows the two disassembled. You'll notice that the AR-7 is a bit shorter what with it fitting into the buttstock, but it is a bit more rotund. And, it's lighter by a bit (but it's a jeep gun, not a backpack gun).

The second photo shows them assembled.

Assembly time is about equal. The buttcap on the AR-7 is a friction fit. In order to make the pad on the end of the shotgun buttstock easily removable, it is held in place by velcro. I have a slip on sling that works on either. The thing must be darned near thirty years old and is still going strong.
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Jeepnik (aka "Old Eyes")
"Go low, go slow, and preferrably in the dark"