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Joined: Sep 2005
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When adjusting Shot Start Pressure, it says to add 7200 psi when using a bullet that touches the rifling. If I am seated .050" off the lands, can I lower this number slightly (say 6500 psi) since the bullet is not quite touching the rifling?
Last edited by altahunter; 03/29/08.
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Joined: Jun 2005
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Joined: May 2008
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You add 7200 psi to the shot start pressure with the bullet touching / in the lands as the bullet has not gained any kinetic energy to engrave itself into the lands - it needs an aditional pressure build up to do this.
At any point off the lands the bullet has started moving, therefore no addition is required.
Strictly speaking, there has to be some small adjustment as a bullet seated 100 thou off the lands will have gained much more energy by the time it hits the rifling than one sat 2 thou off, but in practice it seems to make little difference to the chronograph readings.
Kev.
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Joined: Nov 2006
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You add 7200 psi to the shot start pressure with the bullet touching / in the lands as the bullet has not gained any kinetic energy to engrave itself into the lands - it needs an aditional pressure build up to do this.
At any point off the lands the bullet has started moving, therefore no addition is required.
Strictly speaking, there has to be some small adjustment as a bullet seated 100 thou off the lands will have gained much more energy by the time it hits the rifling than one sat 2 thou off, but in practice it seems to make little difference to the chronograph readings.
Kev. So please help a fella thats just getting his feet wet in the software end of things. The only thing I would be buying software for is pressure. All my guns are old (well most are) so I want to know if a load I'm starting with or currently using is taxing them. Can any of these programs do better that just"add this blanket number"We all know thats a different number,or should be in a cast load 30/30 than a 500 gr FMJ in a 458 lott. If a fellas prime concern is pressure calcs where does he go? Or is it even out there more accurately than what I'm reading? Cause if it aint I can guestimate better
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Joined: Aug 2006
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So, how about Weatherby's that have a lot of freebore... Is there nothing in the program adjusting for that.
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