Colin - thanks for the shooting video. That is a LOT more recoil than I would put up with. Good-on-ya.

500gr. is 18.3 drams, BTW. 12 (4 less than the full load) drams in a 4 bore, broke WW Greener's recoil machine,w hcih recdored up to 200gr. So - 10 drams (273gr.) with a 1,450gr. ball in a 22pound 4 bore, was enough over 200 pounds to break a machine that recorded recoil up to 200pounds without breaking.

Colin is shooting a 3,500gr. ball, more than twice the weight in projectile, with a charge 50% greater and recoil isn't too/too bad. (I noticed he only shot 2 of those 500gr. loads - I wouldn't have shot any - "hey, new owner, time to regulate your rifle"!! Yes- the gun weighs twice as much - go ahead, knock yourself out, have fun with it.
Yowser!