Bulldog, even at 2000 fps the .500 NE is a very obnoxious caliber. Shedding 150 fps does not do much to mitigate recoil.

As for the XMP5744 load, I use F215 primers and NO FILLER and it regulates just fine. 3-4 inch groups at 50 yards are typical, although I could probably improve on that if I tinkered with different lubes and sizing but I am too lazy for that. The bullets are sized to .512".

I tried out some 700 grain cast lead bullets in my .500 NE but they never regulated, and kicked like hell.