What does this great historical target got to do with shooting OFFHAND?
Rowland shot it from a machine rest, using a .32-40 Pope barrell, says so right on the target.
Somehow this thread has gone of the rails. And Schuten style rifles for off- hand are certainly not practical for a hunting rifle, IMHO.
Machine rest....

If it seems too good to be true....
Offhand practice is offhand practice...
Hunting rifle, schutzen, black powder, pellet rifle, or (perhaps best) rimfire.
To me it matters little what I practice with.
At issue here is that we practice on level ground and perfect conditions at the rifle range....If you shoot deer there I suppose that is good.
If the ultimate goal is to be a better offhand shot in the hunting field then my suggestion is to take a rifle into the field and shoot offhand from all sorts of out of whack positions...If nothing else it will show you why we grab a tree, rock, stump, handful of grass, or whatever improvised position.
To me offhand is a last resort.
Most hunters have no idea as to how they can best use the environment around them as a quickly improvised field position. I can't tell you how many times I've seen guys blow perfectly good opportunities when the perfect rest 5 feet in front of them.
IMHO from a hunters perspective this is a skill worth much more effort and practice than offhand shooting.