Way back when I fired a Harper converted Saxby-Palmer Orion Six TAC revolver. I got all six pellets into a 1/2" circle two-handed at 10m. It was totally cool, it even recoilled a little like a rimfire loaded with .22 Short.

The velocity seemed fine, when I asked the owner there was some evasion but finally I got the impression that it was fine because it was putting out 9 fpe!