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+P Loads

Discussion in 'Handloading and Reloading' started by cvo, Apr 6, 2010.

  1. cvo

    cvo Well-Known Member

    Exactly why do they call it a Plus P? If you use a +P case does that make it a + P load?
  2. mesinge2

    mesinge2 Well-Known Member

    +P cartridges have been loaded to a higher internal pressure than is standard for ammunition of its caliber, but less than the pressures generated by a proof round. This is done typically to produce rounds with a higher muzzle velocity and stopping power, such as ammunition used for defensive purposes.

    Compare 38 Special and 38 Special + P, and 45 ACP and 45 ACP+P on this chart.
    Last edited: Apr 6, 2010
  3. NuJudge

    NuJudge Well-Known Member

    Usually, the only case difference between regular and +P is the stamp on the case. The stamp "+P" indicates the cartridge develops higher than standard pressure. SAAMI has standards for "+P" in some calibers, and there are some cartridges marked "+P+" to indicate still higher pressures.

  4. 243winxb

    243winxb Well-Known Member

    No, Starline brass marked +P in 38 is the same as plain 38. But in 45acp Starline +P is thicker in some areas compared to there standard brass. Other brands are different. Follow this link > http://www.handgunsmag.com/ammunition/demystplusp_0306-7/
  5. cvo

    cvo Well-Known Member

    If you took a Starline .45 case in +P and non +P and load the same powder amount in both, would the +P case have more pressure?
  6. 243winxb

    243winxb Well-Known Member

    Yes, start low on the powder charge and work up.
  7. 243winxb

    243winxb Well-Known Member

  8. cvo

    cvo Well-Known Member

    Looking at the Hornady book I have a 230gr XTP .45 calling for 6.6 gr (800 FPS) of Power pistol, so the load would be 4.6, because of the 2 grains less capacity of the +P case?
  9. Ol` Joe

    Ol` Joe Well-Known Member

    The 2gr is "total case volume" water wgt not powder wtg and has no apples to apple relation to the needed change in powder charge its self. The powder charge for the smaller volume brass would have to be determined by testing and working up the load.

    The volume of a standard case may be say 12 gr of water and a 2gr reduction for a +P case will bring that down to 10 gr of water.
    The proper charge for the 12gr case might be 6.6 gr and the 2 gr small could possibly be a whole grain lighter, or maybe the same. If the powder capacity of the case with a bullet seated doesn`t change the usable volume.
  10. Steve C

    Steve C Well-Known Member

    +P is a pressure standard for some cartridges as defined by SAAMI (Sporting Arms and Ammunition Manufacturing Institute) an association of the nation's leading manufacturers of sporting firearms, ammunition, and components that publishes voluntary standards developed by its members. Any pressure over the maximum standard pressure but not in excess of the maximum +P pressure is considered +P.

    Most cartridges do not have a +P loading pressure. Its used mainly for older low pressure and often formerly black powder cartridges that can work safely in modern weapons at a higher pressure than when originally developed.

    The +P designation has only been around for about 20 to 25 years or so. Prior to that high pressure loads sold by the major manufacturers was called Police loads or went under names like the .38-44 which was high pressure .38 spl to be shot in handguns with a heavier frame and cylinder size of the .44 spl but chambered for the .38 spl. A precursor to the .357 mag. Some small and custom loading companies produced higher pressure ammo for police or the self defense market like Super Vel and the still in business Corbon.

    Here's a good article on Wikipedia about over pressure ammunition. http://en.wikipedia.org/wiki/Overpressure_ammunition

    Here is a link to SAAMI pressure standards on Ramshots website:http://www.ramshot.com/powders/loadpressure.php
  11. cvo

    cvo Well-Known Member



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