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Old 12-30-2012, 9:10 PM
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Fjold Fjold is offline
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If you are too close to the lands then seating the bullets deeper will lower pressure. Roy Weatherby proved that with his proprietary cartridges. He stuffed more powder into bigger cases and then lengthened the throats on his rifle so that the long jump to the lands before the bullet meets the lands lowered the peak pressure of the cartridge.

That's the same reason that the 5.56 can run hotter than the 223, the 5.56 has a long throat which lowers the peak pressure. The combustion chamber is larger because the bullet has a lot of room to move forward before it is forced into the rifling.

The peak pressure isn't reached in the cartridge case. And the variations in the size of the pressure chamber due to the seting depth of of the bullet is minor. It takes very little pressure to push the bullet out of the case (a primer alone can do that). The maximum pressure of 50,000 - 60,000 PSI peaks after the bullet hits the rifling as it requires more pressure to engrave the bullet and force it down the barrel.

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Last edited by Fjold; 12-30-2012 at 9:18 PM..
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