To me, ergonomics with sporting rifles means that the rifle has the right combination of weight, balance, length of pull, drop at the cheek rest and heel, and shape to minimize felt recoil and align the eye with the sights.
For example, a Winchester 94 was mentioned as having perfect ergonomics and while I agree to a great extent, it can be one of the worst when a scope is mounted on it, especially the older ones that need a side mount.
I like my rifles to snap up quickly and perfectly aligned. Low-mounted scopes on Remington 700s are close to perfect, but I also like Tikkas, which also have palm swells that feel nice.
My Franchi O/U 20 gauge shotgun is the most ergonomic firearm I've ever handled. It seems made just for me! I can flip the safety off and bring it up in a half-second, pointing perfectly every time. Recoil is well-directed, making a second shot very quick, but not often necessary. I'd thought my Rem semi-autos pointed well, but they are a bit slower to mount and don't down as many clay birds.
“God save us from people who mean well.”
― Vikram Seth