I have an old Hopkins falling block shotgun in 16ga.
The barrel is 1.17 O.D. on the breach end.
I'd like to make it into a rifle. I've considered using a sub-caliber insert, but the chamber is too short for most available ots products.
Does anyone have an old barrel about that might fit with minimal machining? The shotgun barrel just slips in and is retained similar to a Favorite.
I am fully aware of the strength issues, ideally an old pistol chambering, like 45 colt or acp.
I've read about this being done before.
I know it's a long shot (no pun intended) but a lot of us have this kind of stuff laying around. I could pay or trade, but it's a low buck project.

I take it then that you don't have a barrel.
Does anyone have one I might use?

I am working on a project of this nature. I have 4 large frame H&A Shotguns. I know these are "weak" actions
but I am start out,22 cal., but will expend into 25 cal.
I know they are "ugly" DeHaas says so,but I set one of my Hepburn actions next to it , all most the same, dim.? The actions are smooth and simple,parts available and WHY NOT?  . Use the barrel shank as a bushing, my gunsmith made a button shank to mate the 22 barrel to the breech face,the extractor can be extended to reach the 22 with no real eng. OK Why try to make silk purse out of a sow's ear. How about the Martini Henry conversions to 22",big action,little tube?
But mostly to try! Will TRY to do pic's 57thahc

Green Mountain has 25" 45ACP heavy gunsmith special blanks for $54.95 that would work equally well for 45 Colt. At that price, they are hard to resist. I will probably buy one for an as yet unknown future project.

(You need to Login or Register to view media files and links)

John, do you recall what thread you used? As I recall, the receiver wall is rather thin. I have considered sweating a threaded sleeve in to retain the barrel.

JCHannum wrote on Jun 11^th, 2015 at 9:07pm:

I made a special tap with fine threads. I may still have it , will look.

All- also watching with great interest-- I've been sitting on a 20ga break open in good shape to do the same thing in perhaps a small, low pressure cartridge.
This is how a rank beginner like myself gets the knowledge/confidence to come out of the shadows and take a first step!
Chuck V