Well it is my opinion, not any established fact. I probably should have said suitable for modern high pressure cartridges not strength. No doubt about it the 1885 Winchester is the strongest and most suitable for conversion to modern cartridges. The Sharps has a lot of metal for sure but vertical sliding breech block design and firing pin don't lend themselves to varmint rifle calibers. Hepburn is a good design for straight wall cases but the vertical sliding block does not cam and my opinion they don't extract well either. It's probably plenty strong. You hardly ever see Sharps or Hepburn's in Varmint conversions. You do see a lot of High Walls and 44 1/2's converted.
The 44 1/2 is the most modern American single shot action design, 1907, and Incorporated improvements on the older designed actions. It's weak point is the metal and built for 38/55 case head cartridges. Stay with something on that basic case it's a very good Acton. Exception the 1885 none of the single shot actions are as strong as most bolt guns and including the 1885 don't handle escaping gas well at all. They are all good shooters if you understand the limitations and keep the pressure reasonable.
Boats
