Petzal: The Great Overbore Conundrum
Once upon a time, the worst thing you could say to a rifleman was that his cartridge of choice was...
Once upon a time, the worst thing you could say to a rifleman was that his cartridge of choice was overbore. Today this would be the equivalent of calling him a Clintonista, or slapping him. Overbore meant that his 7mm Thunderf***er Magnum burned more powder than it could efficiently use, and was therefore less worthy in the great pantheon of cartridges than, say, a 7×57, or a .280, or for all I know, a 7×64. It also, by extension, meant that the person who shot a 7mm Thunderf***er magnum was unworthy to enter the Kingdom of Heaven, or was just a squirrelheaded son of a bitch.
There were other concerns. Huge cartridges that used gobs of powder burned out their barrels quicker, cost more to shoot, and were more difficult to shoot than non-overbore rounds. This is all quite true. But there’s another side. Sometimes, you want a bullet to go much faster than a standard cartridge can manage, and the only way you can do it is by burning lots and lots of powder. It’s the same in automobiles; if you want more speed, you need proportionately huge increases in horsepower.
An example: My favorite .338 load right now is a 225-grain Barnes XXX backed by 72 grains of RelodeR 19*. This gives me 2,750 fps, which is enough for any shot inside 300 yards. If I anticipate a longer shot than that, I can go to a .338 Remington Ultra Mag, which will gulp down 93 grains of RelodeR 22*, which drives the same bullet at 3,020, making hitting at long range somewhat easier. It is, as even the dullest among you can see, a whopping increase in powder for a comparatively small increase in velocity. But there you are.
Overbore, who cares? They are very useful cartridges under some conditions, and even now, as you read this, people are making RelodeR powder and new barrels whether we want them to or not.
*These loads are safe in my guns, but they may blow you into the next world. That is your concern. I assume no liability from now until the end of recorded time.