mauserand9mm, I contacted ADI in 2011 in regard to this. There recommendation was the 70% minimum load up to 100% (no compression) of a seated projectile. There best estimate was between 1100-1500fps, but I have a 30+" barrel. I do have Trail boss now but have never tried it in my .500NE.
One of the many things I have to experiment on yet, getting to the range is always my biggest issue!
Sorry I can't help you in this regard
Best of luck with the load, but the 440 gn NFB load comes out at 1750fps in my rifle turns pigs inside out!
Cheers
93x64mm