I own two .458 Win Mags. The Browning Safari FN Mauser has a mag for 3.34 or slightly longer cartridges but the CZ 550 has a long mag that allows 500gr and 400gr Barnes to be loaded to 3.6" COL.
There is ample freebore at that length and I can use Lott loads since I now have the same powder capacity.500gr at 2300fps and 5600 ft-lbs of energy.The long 3.6" loads will not fit in the Browning mag but will fit in the chamber(since I am using 2.5" Win Mag brass). This allows me to take my first shot with a Lott equivalent and 3 follow up shots with standard length loads. There is a considerable difference in recoil but when facing dangerous game it is a moot point.