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How to read a pressure curve

Discussion in 'Reloading' started by Snapper2, May 1, 2011.

  1. Snapper2

    Snapper2

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    when starting from scratch. Caliber 400 corbon. new starline 400cb brass. cci 500 spp. Oal-1.189. Bullet 155grxtp. No data for 800x in 400cb so I started close to high end 10mm data . ProChrono results..... 10grs-1254fps.....10.5grs-1324fps.....10.8grs-1373fps.....11grs-1427fps. Fired brass measurements and primers not all that bad. I will not push past 11grs anyway because theres no data from Cor bon pushing 155grs past 1300-1350fps with any powder. The last bump in powder 10.8 to 11grs gave the same 50fps rise in velocity as the 10.5gr to 10.8 did. How do you read this in terms of pressure? Cor bons data for the same with #7 is 13gr-14gr, 1250- 1300fps. Which I've also tested. Seems like a sharper curve at high end with #7?
     
  2. Gokyo

    Gokyo

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    I do not see any pressure data here. I am not sure I would count on velocity to = pressure.
     

  3. Snapper2

    Snapper2

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    Thats what I'm trying to learn.
     
    Last edited: May 1, 2011
  4. WiskyT

    WiskyT Malcontent

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    There simply is no way to know if you are within pressure limits without a pressure measuring device. There is no concrete correlation between pressure and velocity. That doesn't mean your 800X loads aren't safe, it just means you really have no way of knowing without a testing lab.
     
    Last edited: May 1, 2011
  5. Snapper2

    Snapper2

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    Can you tell anything from velocities....ie. which powder burns slower in particular cartridge? #7?
    800x 10gr-1250fps.....11gr.-1427fps
    #7 13gr-1250fps.....14gr.-1300fps
     
    Last edited: May 1, 2011
  6. fredj338

    fredj338

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    You can't read pressures from vel data. Pressures are rarely if ever linear, so even if you could establish a base line & plot a curve, going 0.1gr over max can push pressures vertical. There is just not a lot of room in smaller cases using relatively fast burning powders.
    Sure, you can determine that equal charges of diff powders & one gives a higher vel, it is producing higher pressures. All things being equal, pressure often equal vel. So same bullet, same powder charge wts, higher vel will almost always mean higher pressure. So in your example, AA#7 is acting slower than 800X in the 400Corbon. In most burn rate charts, that is what I would expect.
     
    Last edited: May 1, 2011