4Seventy - measure from the base to the top of the belt - that is the headspace measurement. I have found some to be within .210" to .216", which could be considered normal for SAAMI specs on rimmless brass (.006"), but - those that over that, will still chamber in the rifles, showing the chambers themselves have to much slop in the chamber, which means brass stretched at the web on the first shot. After that, if the shoulder is not touched when sizing, the stretching every shot is limited, but not eliminated and if one does as much shooting as he/she should, means frequent case length triming, until the brass finally goes bright ring and is tossed.

Another good idea for a .416 would be the 8x68S case. We've taken it up to .375 (9.5mm) and received wonderful velocities. It would be closer to a .416Rem. than the .416 Taylor due to having identical case capacity as the Rem. case + about 2 gr., depending on the make of brass. RWS brass is super brass, much stronger than normal belted magnum brass.