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Load Pressure

Discussion in 'Shooting Related Threads' started by Blueraven81, Apr 21, 2010.

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  1. Blueraven81

    Blueraven81 TS Member

    Joined:
    Oct 17, 2009
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    Can someone provide me with a simple explanation about the differences in load pressure? Pros vs Cons, effects ect...

    Thanks,
    Blueraven
     
  2. dverna

    dverna Active Member

    Joined:
    Jan 29, 1998
    Messages:
    2,717
    Powder needs pressure to burn properly.

    Anything below about 7-8000 psi will leave unburned powder in the barrel. Not a big deal if using a break open gun.

    I believe the max pressurepressure for a 12 ga is about 12,500 psi.

    I try to keep pressures in the 8500-10,000 range for Trap loads. For Cowboy Action, where I want very low recoil, I am using 7/8 oz of shot and low velocities - so the pressure is below 7500 psi.

    Pressure has no affect on recoil. A 9000 psi load that moves at 1200 fps has the same recoil as a 10,500 psi load at the same velocity.

    Simple rules - A heavier payload using the same amount of powder will always give higher pressure. The same payload with more powder will always give higher pressure. Reducing case volume will give lower pressures (more for rifle or pistol loads - but also explains differences between straight wall and tapered shotgun hulls)

    Don Verna
     
  3. Quack Shot

    Quack Shot Active Member

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    Mar 14, 2006
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    4,003
    You need enough pressure for the powder to burn normally and a low enough pressure to prevent putting excessive strain on the firearm. I keep my loads UNDER 10,000 PSI (NOT LUPs). There are a few exceptions for special hunting loads. A steady diet of high pressure loads can cause trouble over time. A few might not cause issues unless they are severely overloaded. I keep the lower limits around 6500 PSI, depending on the powder and load. The SAAMI Maximum for the 12ga 2 3/4" shell is 11,500 PSI as far as I know. It may be slightly higher for the 3"" and the 3 1/2". Loading under 10,000 PSI leaves a little headroom for error and variables such as Temperature, Crimp Depth, and component variables due to manufacturing, etc. It does not take much to push a load another 1500 PSI. Leave the shells in a hot car and you could very well be over the top.
     
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