Quote:
Originally Posted by 125JHP
OK, so for a given cartridge, bullet and gun does equal pressure equate to equal velocity regardless of the powder? In other words...
if it takes Xgr of powder A or YY gr of powder B to achieve 900 fps will both loads be generating the same pressure?
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NO
Its not just pressure but PEAK pressure and pressure duration.
Think of it this way. The total energy put into/upon the bullet will determine its vel when it exits the muzzle.
If you load a extremely fast powder, lets say Bullseye, the powder builds to a rapid spike and then tapers as the bullet does down the barrel.
A slow powder, 296 for example, requires a heavy crimp because the powder actually begins to burn in the case and builds pressure for a micro second before the bullet exits the case. This pressure stays constant the entire time the bullet is in the barrel, and in fact a longer barrel allows more time for the pressure to act on the bullet. This is why longer barrels with MAGNUM loads give higher vel., think 20 inch rifle barrel vs. 6 inch handgun. Longer barrels with non magnum loads, think .45 ACP, give very little vel increase.