That is indeed a good fix. I was just trying to do the least to change a very expensive antique. Your fix while it works great would significantly lower the rifles value and get me the smith in a heap-o-trouble,, if the rifle was a new model, it's great. After going back over some records I found I'd fixed one with a similar problem. I drilled and tapped a small hole in the barrel where the retension hole is, threaded in a screw and peened it in place. Then made the hole in it. Very little shows and the fix can be easily repeated should the problem come back. It shouldn't though as I case hardened the screw(plug?) before it's last installation.