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FrankenMauser · May 1, 2015, 05:08 AM

Most high velocity bullets "self-destruct" because of centrifugal forces.
Since centrifugal force can be controlled by the designer, via twist rate and velocity, it's easy to negate the "mid-air lead puff".

All else being equal:
As velocity increases, twist rate decreases (slower twist).
As twist rate increases, velocity decreases.

That's why .22-250s and .220 Swifts often have 1:12" or 1:14" rates of twists, while .223 Rem, .222 Rem Mag, and similar cartridges are more commonly found with 1:7" to 1:10" twist rates. The reason for the difference is velocity.

With a little bit of digging in my library, I found a reference to the cartridge being used by some guys in Georgia, trying to break 5,500 fps. After determining what the maximum load would be, they ran pressures up to 68,000 psi and could only reach 4,900 fps. The throat was completely fried with fewer than 20 full pressure loads fired. (So, it's definitely not great for longevity.)
They tried pushing the cartridge to 70k psi, but "encountered brass flow issues."
No type or weight is mentioned for bullet or powder, so I'm not sure if that would be a realistic maximum for the cartridge, or just for their set of parameters.

May 1, 2015, 05:08 AM	#2
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,456	Most high velocity bullets "self-destruct" because of centrifugal forces. Since centrifugal force can be controlled by the designer, via twist rate and velocity, it's easy to negate the "mid-air lead puff". All else being equal: As velocity increases, twist rate decreases (slower twist). As twist rate increases, velocity decreases. That's why .22-250s and .220 Swifts often have 1:12" or 1:14" rates of twists, while .223 Rem, .222 Rem Mag, and similar cartridges are more commonly found with 1:7" to 1:10" twist rates. The reason for the difference is velocity. With a little bit of digging in my library, I found a reference to the cartridge being used by some guys in Georgia, trying to break 5,500 fps. After determining what the maximum load would be, they ran pressures up to 68,000 psi and could only reach 4,900 fps. The throat was completely fried with fewer than 20 full pressure loads fired. (So, it's definitely not great for longevity.) They tried pushing the cartridge to 70k psi, but "encountered brass flow issues." No type or weight is mentioned for bullet or powder, so I'm not sure if that would be a realistic maximum for the cartridge, or just for their set of parameters. __________________ Don't even try it. It's even worse than the internet would lead you to believe.