A good friend here shoots one. He gets exactly the same velocities, verified on a chrony, as published factory speeds for 7RM, using H4831SC and 140 or 160gr pills. With lots less powder than 7RM, and no signs of pressure in the cases at all.
His rifle is also very accurate... bughole groups.
I think 280AI is the sweetest of all the 7mm cartridges. If I hadn't come across the excellent 7-08 I'm shooting, I'd have one.