Ballistics Question

[Jimmybacon43]

What would happen if someone were to manufacture a 5.56x51mm Cartridge? So, not just a 5.56 bullet in a .308 casing, but a stretched out 5.56 casing that is proportional in diameter to the original 45mm casing, just longer.

Idea would be to get a higher velocity round, why has no one done something like this yet? I'm assuming it would create too much pressure?

[-hanko]

What would happen if someone were to manufacture a 5.56x51mm Cartridge? So, not just a 5.56 bullet in a .308 casing, but a stretched out 5.56 casing that is proportional in diameter to the original 45mm casing, just longer.

Idea would be to get a higher velocity round, why has no one done something like this yet? I'm assuming it would create too much pressure?

google 22-250...you'll be close

[Fjold]

The 222 magnum is a longer case in that diameter but not that long. The long, narrow cases don't seem to be as accurate as the shorter fatter rounds.

[russ69]

The 222 Mag is 47mm long I believe. It's actually a good cartridge but it's not a very popular one. It's too long to cycle through an AR15, I think. It was designed in the 60s.

[billt]

Increasing case capacity in relationship to bore size gets to be a law of diminishing returns. You can see this more clearly with the various .30 caliber Magnums that have come down the pike lately. Cartridges like the .30-378 Weatherby and .300 Remington Ultra Mag burn tremendous amounts of powder compared to more efficient .30 caliber Magnums like the .300 Winchester Magnum propelling the same weight bullets.

They deliver very little in velocity gains when compared to this massive consumption of powder. This also causes a lot of throat erosion and barrel wear. The most ridiculous of all of these "Wonder Magnums" was the .223 WSSM. The cartridge was so over bore it was showing severe signs of barrel erosion after just 400 rounds in several gun tests. That's just insane when you consider a Chrome lined .223 / 5.56 MM barrel that is well cared for will last for literally thousands of rounds. All with little velocity loss compared to the .223 WSSM.

The more this theory is applied, the worse it becomes until you are gaining little to nothing by going even bigger with case capacity. And when you factor in that there is nothing a .30-378 can kill that a .300 Win. Mag. cannot, it all becomes even more pointless. Which is why these calibers are not more popular. They are more for "the guy who has everything", and wants to play around.

[RobertMW]

Increasing case capacity in relationship to bore size gets to be a law of diminishing returns. You can see this more clearly with the various .30 caliber Magnums that have come down the pike lately. Cartridges like the .30-378 Weatherby and .300 Remington Ultra Mag burn tremendous amounts of powder compared to more efficient .30 caliber Magnums like the .300 Winchester Magnum propelling the same weight bullets.

The more this theory is applied, the worse it becomes until you are gaining little to nothing by going even bigger with case capacity.

Unless you start increasing barrel length. If you were to shoot those overbore cartridges out of 26-32" inch barrels with good powder selection, suddenly you would see those leaps and bounds.

Nobody wants to haul a 30+" inch barrel on a hunt though, and there are no competitions that would require such a rifle either, as most extreme range shooters already use the big military calibers.

[dskit]

220 Swift is pretty darn close.

[dc2allday]

Jimmy are you trying to get schooled here?

[CK_32]

There is a ton already. The list of exotic or non conventional cartages is phenomenal. Many get lost in the sea of calibers tho. Example some listed above you and many here, my self included have never heard of.


Also not just the case/bullet choice but each manufacture bullet design and their individual BC comes into effect as well. Look at 308, look at all of the match and standard bullets given just for the 168/175 and 155 designs. All have different BC numbers and values in the same caliber design.