Here's a comparison for you. Your barrel is leaving roughly .1625" of steel. (.825-.5=.325, divided by 2). I have a 58 cal on a 15/16" barrel that leaves roughly .184" of steel (15/16-.570= .3675, divided by 2). That's some thinner than what you find in current 1" barreled 58's, but back in the 70's was deemed plenty sufficient.
I did some checking and in those days a 100 grain charge of 2f was considered a safe max with round balls in that light barrel. I tried 100 but backed off to 80, not only for a little extra margin of safety but also for comfort. In such a light gun with a hooked butt, the 100 grain charge was a little starchy for my taste. And it's still whopping plenty for deer, even if the trajectory is a little too loopy for my taste to make it a 100 yard gun. So be it. I hold my shots to 75 with any gun.
You can probably dig up some "official" recommendation of loads for that barrel somewhere in someone's archives. Nice to know, but like the others I have to believe you're plenty safe at 70 with RBs. That's more than plenty for deer, and probably flatter shooting than my 58 with 80. And it's going to be a whole lot more comfortable than heavier charges in such a light gun.