I emailed HSM and they answered:
1.635"
HS Munitions Inc
4406 Rathbun Lane
Stevensville, MT 59870
406-777-2106 x115
Fax: 406-777-3908
www.thehuntingshack.com
Awesome! Thank you so much. I believe that they just might work.
I too contacted them on Friday or Saturday (using their "contact box" rather than email, so I have no email copy) but I think that I just asked them if the cartridge was compatible dimensionally with the Rossi 92 action. They didn't answer, but your more specific question certainly worked well. Thanks again. I'm picking-up a box of them in Calgary on Thursday, and will post the results when I get home. In the meantime, I'll try to research the Rossi-spec maximum OAL. It'll be close, but that chunky slug profile might be a deal-breaker.