Old thread worth reviving. I recently got a case of magnum-itis myself, and have played around with 264 Win Mag, 7mm Rem Mag, and 300 Weatherby Mag. Fast, accurate calibers, the downside is more recoil, and muzzle blast, and more expensive to reload, because they burn a lot of powder.
Looking at my reliable albeit somewhat dated Hornady hardcover reloading manual, something becomes quite clear- the 30-06 is a very efficient cartridge, and hard to beat for all-around use, esp. for N. American game.
the other 300 cal. magnums burn a lot more powder, to get the same velocity as a hot 30-06 handload. For sake of comparison, look at the '06 with a 150 grain bullet at 3000 fps. Compared to the magnum calibers and how much MORE powder they burn, to do 3000 fps, it's obvious that beyond the 30-06 case size, magnum cases exhibit diminishing returns, compared considering how much more powder they burn.
Even the oft-touted "highly efficient" 300 H&H burns more powder to get the same velocity. Let me clarify, a starter load for a 300 magnum, equals a hot load for a 30-06. But the truth is, magnum shooters who do a lot of target shooting, load the magnums down anyway, to reduce muzzle blast, recoil, and cost. So basically one ends up with a huge case with less powder in it, at 30-06 velocities anyway.
here's how they stack up, using IMR 4064 powder, and 150 grain Hornady bullet, at 3000 fps. The 30-06 is safe maximum pressure load, the other 300 magnums listed are the recommended starter loads, all from the same manual, to attain 3000 fps. In the case of the 300 Wby the lowest velocity was 3100 fps.
30-06 52.6 grains (maximum load)
300 H&H 56.1 grains
308 Norma 59.6 grains
300 Win. Mag 61.4 grains
300 Wby. Mag 68.9 grains (3100 fps)
as you can see, the 30-06 gives the same velocity with a lot less powder, to attain 3000 fps, with the same powder and bullet. In the case of the 300 Win Mag, it will burn 20% more powder to just equal the 30-06 maximum load. The reason for this phenomenon is, what I like to call combustion chamber size, to borrow some engine terminology. The magnum case is larger, so the exact same powder charge from a smaller case, will give a lower pressure output in the larger case, because there's more space to relieve and lower the pressure, in the larger case, to begin with. So more powder must be burned to create an equal amount of pressure, in the larger case, to start with. Then beyond that point, even more powder added, to make velocity gains beyond what the smaller case can attain.
so the question becomes, if I already have a trusty old 30-06, why should I even bother with any 300 magnum ? Why not just load up the 30-06 to full potential ?
For many decades during the first half of the 20th century, 3000 fps was considered the "magic number" entry level into high velocity, hence the old "250-3000" name on the 250 Savage, albeit with an 87 grain bullet. Their original goal was a 100 grain bullet at 3000 fps, which was considered optimum for most N. American medium game. That can be attained in a 250 Savage easily with handloading.
With the 30-06, you basically have a "30-3000" using a 150 grain bullet, without being a belted magnum, on a standard length action, and burning as little powder as necessary. Most don't realize just how good the 30-06 is, and that included myself.
yes, the 300 mags can be loaded up to 3400-3500 fps or more, but for sake of the comparison, the 30-06 is a highly efficient round, and hard to beat. If one wants to try out a 300 magnum, just load a 30-06 to maximum safe pressure loads, and you're basically there, for all practical purposes.
Jack O'Connor was well aware of this, and cajoled other hunters who were carrying the 300 H&H, that his 30-06 with his own handloaded ammunition, had the same power and velocity. At the time, he was right, the 30-06 could be handloaded to match the very early 300 H&H factory loads.
I'm sure with some diligent load development, one can get more than 3000 fps from a 150 grain bullet, in an '06, with all these modern powders and bullets we have now.
having said all that, there's just something about that big, belted magnum case, that makes any shooter want to try it out, at least once, or a few times. The only way a magnum makes practical sense, if with the heavier bullets, and very long range, against the biggest of animals- as some previous posters mentioned.
