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Discussion Starter · #1 ·
My Googling has left me unsure of something. Are +P and +P+ specific pressures regardless? Or are they relative pressures based on caliber, bullet weight or some such factor?

The very last thing I read said +P+ SAAMI (sp?) was some given amount, but I couldn't tell if that was referring to figures within a specific situation.

Thanks a million

JimL
 

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From what I know, +P is a pressure rating. It runs from the top of the standard pressure to the top of the +P rating. Now +P+ is usually simply beyond the +P range. But there is usually a ceiling I think but don't quote me on this.

For example (these numbers are simply made up) an 11mm Ghetto Blaster might have standard pressure rated at 27,000 psi. The +P loading would then run from 27,001 psi to 32,000 psi. The +P+ would be from 32,00s psi on up.

Steelheart
 

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Yes, SAAMI has pressure standards for +P and +P+. Loading manuals will usually tell you these limits, or the Speer manuals do.
 

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Discussion Starter · #4 ·
NativeTexan said:
Yes, SAAMI has pressure standards for +P and +P+. Loading manuals will usually tell you these limits, or the Speer manuals do.
Thanks. I'm not getting my (non-loader) question across. Maybe this is a hare brained idea question, but it's theory, not an actual loading question.

Someone said with identical loads pressures would vary based on actual bullet weight - a heavier bullet would build more pressure because it takes longer to get out of the way, allowing more pressure build-up. If I could magically replace a standard 230 grain bullet in a .45 cartridge with one, say, half that weight (without changing the load) would the result be easier on the gun? Or would the lighter projectile make no difference, because the powder load is the same?

Thanks a million

JimL
 

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Yes, a lighter bullet with the same powder charge as a heavier bullet will result in less pressure. For instance, I load a 158 SWC .357 in front of 14.5 grains 2400. If I stick a 140 in there, I go up to 17 grains. 14.5 grains is too light and doesn't produced enough pressure for 2400 to burn cleanly using a 140 grain bullet.

At some point with slow powders loading really light charges, there are those that claim the powder can detonate, that is explode instead of burn, and produce catastrophic kabooms, but those are really light squib loads and usually applies to rifles as I understand it. Normally, less bullet weight produces less pressure, all else being the same.
 
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