I am also surprised you achieved over 1,900fps for the double ball load. I would not have expected that.

If you get an air space between any of the balls, you stand a very good chance of losing your left hand - and maybe eye sight - or worse as well. I would not do it, myself.

If you want to shoot round balls into bears, buy a Lyman GPR in .54 and revel in having one of the best large game calibres there is. .54's work very well on everything up to and incuding elk and moose - even at ranges in excess of one's ability to hit them correctly as I witnessed a hunter pull off many years ago - 170yard bull moose. Piled up in a 40 yard dash.