I don't think you will ever get it, whether "killing power" or relatively small differences in trajectory--which don't matter much with LRFs. Even in the 22" barreled .338 I hunted with for a dozen years from Alaska to Africa my 225-grain handloads got around 2850 fps. So what? That amounts to maybe 1-2" difference in trajectory than your handloads at 400 yards--which makes zip difference on even deer-sized game.
One of the things I also noticed about the .338 (as other experienced hunters have) is that on average it didn't kill any quicker than smaller cartridges. The very first big game animal I killed with mine, using a 250-grain Partition at around 2700 fps, was an eating-sized mule deer buck shot at around 60 yards in a quaking aspen thicket during the last week of Montana's 1988 rifle season. There was about 6-8 inches of fresh snow on the ground, and I found the tracks of a small herd and could follow them pretty much silently.
Eventually got an angling-away shot at the buck, and aimed for the rear of the left ribs. At the shot he didn't even react, just kept walking along until he went behind another group of aspens. Found him there dead, 60 yards beyond where I'd shot him, and the bullet had opened nicely and exited through the right shoulder.
Also killed a 58" Alaskan moose with a 230-grain Fail Safe bullet in 1996 (The Fail Safe acted just about exactly like the Barnes TSX.) The bull was standing on the high bank of a mid-sized salmon river, angling toward me. Put the bullet inside the left shoulder, and the bull reared up on its hind legs, then rolled down in to the flat gravel bank along the river. But then he got up and staggered into the river before I could shoot again (while the guide was emphatically saying, "Don't shoot him in the river) where he died in the middle of the deepest water, only the two tines of one antler showing above the surface.
I managed to get a rope around the antler, and then we dragged him downriver with the guide's jet-boat to the shallower riffle below the pool. We then spent five hours butchering the bull from the top down, surrounded by a cloud of mosquitoes, and after removing every 50 pounds or so of meat heaved the bull's carcass a little closer to the bank. Recovered the Fail Safe, retaining 96% of its weight, lying against the front side of the bull's pelvis. Oh, and there was a hole through the top of the bull's heart.
Could go on at length with similar examples from North America and Africa. Eventually came to the conclusion that the .338 didn't kill any quicker, on average, than the .300 Winchester Magnum, or even the .30-06 using bullets of the same make and similar sectional density. Some other very experienced hunters have also suggested the same thing, including one well-known Alaskan brown bear guide. All of which is partly why I eventually decided even larger caliber, heavier bullets do better on larger game.
I would bet RinB has killed far more big game than you, especially dangerous. He grew up in Idaho when mule deer were very abundant, and killed a B&C buck when very young--along with a bunch of other game. He's also hunted in a lot of other places for since, including taking five Cape buffalo this year alone.
