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Originally posted by ShootinSpirit:
What qualities must a load posess in order to be labeled +P?
It has to do with velocity and pressure the round is loaded with. See my thread which 9mm ammo for some more discussion on +P versus standard pressure. I don't know what the exact spec in FPS or PSI is but one of the guys here should be able to tell you.

Also, +P does not apply to every caliber. For example .357Mag, 10MM, and 40S&W are already loaded on the hot side so there is no +P I believe with these.

I realize this is only basic info but it should give you a general idea. Hopefully, some others who handload and study ballistics can give you more detail.
 

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It relates specifically to pressure. There is an American industry standard pressure; the average maximum working pressure for each cartridge that is produced. A "+P" or "+P+" are steps up in the maximum average working pressure. Increased velocity does generally result - but not absolutely. Some +P loads sometimes, although rarely, do not produce more velocity than the standard loads of other manufacturers. This is probably in cases where the standard load uses a better powder, where the increased efficiency and particular charactaristics increases velocity without a significant average pressure increase.

The europeans have a similar standard. They use metric pressure measurements, and their standard pressure loads may differ alittle from those made in the USA. Norma and Fiocchi are two that come to mind. Though I am not 100% sure that some of their "hotter" loads produce more velocity because of better powder as opposed to simply loading them to higher pressure standards.

Of course they have to take into account that even the same make, model, and batch of any given firearm have very minor dimensional differences in chamber and bore within a tolerence, not to mention the variances in the components of the cartridges themselves. So chamber pressures may very slightly from gun to gun, especially between different manufacturers.

Talking of industry standards for cartridges; isn't it interesting that the industry (as in private) has done this for a very long time. It has done the same for the firearms that use them - all without any government involvement or "regulation". At least up to now where States like California have introduced those assinine and meaningless test standards to "save us" all from cheap affordable guns. I suppose the California legislature was concerned about the idea of poor people being able to defend themselves.

But then certain elements in our government(s) do have a subtle way of subverting civil liberties without actually coming right out and saying that is what it is doing.

Oh ... how I LOVE big brother!

[This message has been edited by LAK (edited 09-22-2001).]
 

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ShootinSpirit, good question. I have yet to get a solid answer on the topic. The +P of one is not the same as the other, as you may have read. A read WaltherP99man's other thread and that did nothing to clarify the issue except to say that there is seemingly little clarity. So far, all I have gotten is that +P means more pressure for a given brand over its standard, but there is no scheme as to indicate just how much more that is, even on a relative scale.

I would really liked to be corrected on this if I am wrong. So far, I have depened on published results to see if +P loads really perform at higher speeds. For .45 defense, I only go with +P loads that are for lighter projectiles (say Hydradrshok 185 gr +P) and shorter barrels. Normal Hydrashok in 230 gr seems just fine out of a 5" barrel, comparatively speaking.
 

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The top of the scale for pressure in 45 acp is 21,000 CUP, I believe. So it should be ammo loaded to about that level of pressure. The problem comes in when you add different lots of ammo, different conditions and different weapons...All of which bring their individual idiosyncracies to the table. What is +P in my weapons may NOT BE in YOURS!!
If there is any doubt...don't fire the rounds...

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!!!Molon Labe'!!!
 
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