Originally Posted by Bullman
Oh, and I read an article on this. they had a device that had a number of insertable rifled tubes you could put in the barrel, let you fire different rounds , some pistol,some rifle. The bad part about that was that it was only about 7 inchs worth of barrel inside your 12 gauge tube, so I doubt you were getting a whole lot of benefit from a 308 fired from a 7 inch barrel.
With no manual barrel selection that idea loses some utility.