Hi, welcome.

This is the load I used in my Holland U/L Hammer 500/450 Nitro.

It is the same (or similar) load to what is in Graeme Wrights book
Shooting the British Double Rifle" - which isn't surprising as it was
Graeme Wrights gun !!!

Case Primer ADI Powder Gns Bullet

Bell Fed 215 2213 100 480 gn Woodleigh

I am not sure which country you are in so if someone here knows which powder
is the equivalent overseas for ADI 2213, could you please post the answer.

I would start a bit below 100 grains - say 96 - 97 grains.

Hope this helps and good luck.

Post again if you have any other questions.

500 Nitro