Shotgun barrel inserts are nothing new. There are several varieties available from simple reducers to competition Skeet tubes. (If you really want to shoot something with big sub-sonic bullets, consider a modern 12-ga repeater with a rifled slug barrel, work-up reduced slug loads, and forget about the .45 Colt. Of course, it wouldn't work with an internal can, and I suppose that's your main idea.) Google Purbaugh tubes to see how the extractors were done before captive extractors became the standard. I agree, a 10-ga would be easier for the can work.
Last edited by zippy13; March 26, 2012 at 11:29 AM.