I should have specified that the 416 Rigby belongs to a friend of mine. He uses moderate loads for it, so that is what I can shoot.

I am still not certain about the recommendation to start with heavy 470 loads and then switch to lighter loads. That seems counterintuitive. I do agree that after shooting the 577 off a bench the 470 would seem light.

I did buy several pounds each of the IMR4831 and RL15. I understand that the recoil will be heavier with the IMR, although I must admit that I am not certain why that it. As soon as I confirm that the RL 15 regulates, I will stock up on it and use the IMR for something else.

Will