My first hunting load for the .458 Win was 74 grains of H4895 under the 450 grain A-Frame in Win brass. It was compressed so heavily that seating the bullets collapsed the odd case. Velocity was a tiny bit over 2200 fps, and groups would cut cloverleafs once in a while. 10 Australian buffalo dropped to this load.
When I finally got some A2230, the same velocity was achieved with 74 grains and no compression to speak of. Pressures seemed very mild, so I creeped the charge up a grain at a time until I got to 2350 fps at 78 grains. The same 9 cases were loaded 6 times apiece at this level, extraction was effortless and the primer pockets were still tight, but anyone trying that load is on their own.
Still haven't shot a buff with the faster load, so whether it will make any difference is debateable.
