Tried it in my Marlin 336CS, it didn't like them as much as the Rem 200gr CL. It REALLY likes the Remingtons. REALLY.
I haven't tried them in my Rem 141 (24" bbl), have heard other's had good luck. I emailed Hornady if it was ok in older guns, never got a response.
Also, haven't hunted with them, yet, so I can't comment on effectiveness.