I did a similar thing when chronographing my .69 back in the 1980's. I'd gone to 200gr., achieving 200fps with a patched .682" ball.
That kicked quite enough, I thought, although not really excessive. I picked up the the 165gr. measure and dropped in a load for a retest.
Yes, talking to the bloke I was teaching about muzzleloading and shooting. I inadvertently dropped in a second 165gr. for a total of 365gr. 2F
and loaded the patched .682" ball. I sat down on the log chuck I was using for a seat, leaned over my "gopher" table and touched it off. THAT
was excessive. I ended up standing behind the chunk of wood that was my chair. Good thing my form was "poor" as my feet were behind "the
chair". The recoil had lifted me up to standing. Now, was was a lot lighter back then, but not a wall flower & as a very strong 190pounds.
The velocity recorded had gone up a mere 70fps over the 200gr. load. At that time, I was getting 1,550fps from 165gr. 2F. That was my moose load.