Graeme Wright’s book “Shooting the British Double Rifle” has a very useful chapter in the Third Edition on loading for Paradox guns.

I have not seen the Fourth Edition that has recently been published but I anticipate it will have as much information or more.

His books sell out fast and then go up in price second hand.

I believe Rigby’s are now offering the 4th Edition and I suggest you go online and buy one whilst you still can.