At H&R's request I sent pics of my hammer mods and the old style low spur hammer to them for their R&D on a new hammer and extension, I don't know if or when it may be adopted, but a low hammer spur and a current style hammer extension may interfere with the barrel release when mounted on the right side, I had that problem on my 35 Whelen Improved, moved to clear the barrel release, it hit the back of the frame before full travel, I ended up modifying the barrel release. The Win M94 style hammer extension is what I recommended, it's lighter and likely less expensive to produce. From previous input on hammer material, it's likely sintered iron(powdered metal).
Tim