In my Rigby,

Hornady's factory 400 grains about 2300fps and high right compared to all my other loads and kick noticeably harder.

410 grain Woodleigh's 2450fps: 400grain Hydros 2550fps-exact same powder charge and primers in both.

400 grain Bertram's 2450, 400 grain Frontier, I have not Chronographed.

The Woodleigh soft and Hydros are same point of impact. The other groups overlap the Woodleigh's group.

This in a CZ550.

The 416Rem really needs a magnum length action to get the best out of it. However all Remington did was take out the middle action screw, remove the area in the mag well that the screw attached to so lengthen the mag box about 3 or 4 mm. I do not know the exact amount. They did this with the 8mm, 375H&H, maybe others.

By "getting the best out of it" I am simply talking about being able to seat bullets way out to the maximum velocity with the widest range of powders. Is this needed, no.