Dave-
First things first, know my best wishes are with you and your family, hoping your wife's doing well.
On the 20-bore
With the handful of light bore-rifles I've gotten running, one trend has shown up with each of them during load development.
With the same bullet weight, adding powder brings the point of impact together, from there adding more brings them down.
If you're seeing a significant amount of crossing, I'd suggest your next move would be to either add bullet weight or bring the charge down.
Heavier bullets will give a more substantial initial recoil impulse, swinging the gun in the direction of the barrel fired (and up).
Heavier charges of powder tend to decrease barrel time (higher velocity) getting you less swing during the 'internal ballistics' microsecond of firing the gun.
Hope that makes sense.
That's just simple and general, and your gun may or may not follow the pattern. I've heard from quite a few other guys that their bore rifles tend to behave in a similar fashion.
A .620 ball of pure lead will weigh about 359grains
You're running a somewhat heavier conical.
Is that the NEI mould you're using?
Try backing off the powder a bit with that bullet and see how it prints.
Even at 1200fpsMV it'd be a great deer killing gun.
Also consider trying roundball in your load development.
Good luck with getting the gun going.
Cheers
Tinker
