I suspect that 500gr. is being punched out of a 22" or faster twist?

That is power - 2,550fps with 500gr.! OWWW and WOW - and from a rifled shotgun! If of standard 35" ro 36" twist, I'd be staying with something lighter than 360gr. and probably attempt to get an accurate load with the 300gr. Nosler - that should work about the best wouldn't it?

Looks like I'm going to have to come up with a box of 3.5" plastic and break them down to do some testing. My torn shoulder is hurting already.