I've owned a couple rifles in 416 rem, and the last one I had built into a 404 J about 10 years ago (maybe a little longer ago than that even, but just can't recall exactly).
I had no problem pushing 400 gr bullets from the 416 cal at 2450 fps(clocked) with 82 grains RL-15.
The 404 will easily push the 400 gr pills at 2500 without breaking a sweat if you want to. It is obviously of larger bore diameter and has slightly more case capacity (5%-7% IIRC)than the 416 when measured to the bottom of a seated bullet, depending on brass brand.
My 404 is on a M-70 CRF action with a Krieger barrel. I get just under 2500 fps with 400 Woodleigh SP's or Barnes X and 84 gr RL-15.
The thing that is really nice about the 404 vs the 416 is that there is no belt and the case feeds so nicely.
