I have a gudgel dummy launcher that mounts on the end of a shotgun using the choke tube threads and fires .44 magnum blanks which supposedly can be reloaded.
The manufacturer is no longer in business, even though they still have a website
I've found the launcher to be very helpful in teaching dogs to swing with the gun.
Do any RTF folks use one of these? If so, how do you handle reloading the blanks?