[Smitty901]

Disclaimer, I have use something like this in the past. It worked.
From a preper stand point flexible is important . I am not recommending it just pointing it out
Gauge Adapter system for 12G allows a single shot 12G to be used with 11 different calibers.
Single shot yes still better than no shot. I don't expect them to sellout over night.
http://www.prepperforums.net/forum/newthread.php?do=newthread&f=90

 

[1895gunner]

Here is a link to a video..

1895gunner

 

[PaulS]

I have made things like that before - My brother has a 410 adapter for his 12 gauge that I built. He tells me that the 12 gauge choke even keeps a decent pattern with the 410 shell.I have thought about making a full length adapter to fire 223 from my 20 and 12 gauge single shots.

 

[Infidel]

I saw these on another forum and was reminded of the old Briley Tubes. My father had a set of them and he could use anything from .410-12ga in his O/U. My only complaint with this setup is he length of the barrels. Firing .223 or .308 out a 7" barrel seems kind of silly to me but I guess if you didn't have anything else it would do in a pinch.

-Infidel