I shot hundreds of rounds of those 3" shells with 1.75 oz of #6 shot in competition and for hunting and a much lesser number of the 3.5" shells. I can't give you any numbers but at the time, they were some of the best shells I'd ever shot. Most of us shot them through very tight chokes, in the .640 to .650 range.
I let a friend have the last case of those shells that I had a few years ago. While I have not shot any of them through a JEB'S choke, I suspect that they'd be deadly in a .650 or .655 JEB'S.
Thanks,
Clark