Hi,
If it’s any help I have the ballistic products manuals, the “small bore” manual for example has single USA lead buck #000 (67gn) at up to 2850fps in a 2.5 case, @10800 psi, however this is using “lil’gun” powder, I only load lead shot for the hushpower 410 myself at 19gm with this same powder to 1100 fps.
Best
Dave