I have owned various and numerous 300 magnums over the last 45 years or so, and I have killed game with most of them. I still have a 300H&H, a Mauser made by me with a long barrel. I had another one, a pre-64 M70 Winchester for many years too. I have used and owned several 300 Win mags, Three 308 Norma mags One 30-338 mag and a 300 Weatherby.

I have sold all my 300s except for my custom Mauser.

I can't say I ever saw ANY difference in how any of the 300s killed, and that should not surprise anyone.

They all shoot the same bullets and they all shoot them fast. The widest spread of them all was my 30-338 with a 22" barrel and the 300 Weatherby I had with a 26" barrel. But the difference of about 120 FPS is the same difference in shooting an animal at 80 yards with the Weatherby and one at 175 yards with the same gun.

Said another way, the short 30-338 and the long Weatherby are only 120 FPS apart and a 180 grain bullet from the Weatherby is at the same speed as the 30-338 at only 85 yards.

We don't usually have total control of the distances we shoot at game, so any theoretical advantage of the Weatherby over the 30-338, (or the 308 Norma, or the 300 Win mags or the 30H&H mags) is just that. Theory.

When theory and fact disagree it's very easy to say which one is wrong.

But the real world of hunting showed me there was really no difference at all. In fact there is very little difference in the kills I have seen, and the kills I made myself between my 30-06s and my 300s.

So I sold all my 30 calibers larger then my 30-06s except the one Mauser 300H&H, and the reason I kept that one is just because I REALLY like the rifle. It's very accurate and very effective and it's made with the back and the front of the magazine lengthened, so I can load my rounds with the bullets out farther than most 300H&Hs. That gives me the same velocity as the Winchesters I owned, and with this H&H the velocity is within 20FPS + or -. With one load, firing 200 grain bullets, my H&H is actually a bit faster then my 300 Winchester's were.

But with that said, the only up-side I ever saw with a 300 over the 30-06 was a bit flatter trajectory. I never could see any added killing effect on deer, antelope, elk, or moose. My experience says a 300 is not a better killer than a 30-06. It's a 30-06 with a bit longer range.

Maybe the reason not too much was written about the 300H&H was similar to what Taylor said about the 9.3X62.
It was just a "given" that it worked, and worked very well. It was so reliable and consistent that there never was much to get a pro vs. con conversation going about one.

Assuming the use of good bullets that exactly how I see the 30-06 and all the 300 mags.