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Understanding 9mm +P Ammo

Talyn

Talyn

SAINT
Founding Member
If you’re new to the world of ballistic self-defense, there are a few critical things you should know about how your ammunition works. The first thing to understand is that there are several basic kinds of ammunition.

When you’re looking for self-defense ammunition, many people have the mistaken belief that 9mm ammunition with the +P label is ammunition with “more power.” That’s not correct; the +P means “more pressure”. More pressure can translate to more power, but that does not necessarily correlate to increased lethality or stopping power.

Understanding 9mm +P Ammo

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It’s also important to note that there’s “+p” and then there’s +P.

Most of the major ammo manufacturer +P rounds are just barely over the SAAMI limit for standard pressure—say, 9mm +P will be at 35500-36000psi, when the top end of +P is actually 38500psi (if I recall the correct pressure correctly). Then you have the more boutique manufacturers—eg, Doubletap, Underwood, Buffalo Bore—that are pushing the pressure north of 38k.
 
Hi,

Is it true that you need to use a longer barreled pistol (5" or 6") to really take advantage of the increased velocity/accuracy of +P ammo? I seem to recall reading that in 4" or shorter barrels there's just not enough length to let the charge burn completely and build up to full pressure before the bullet exits the muzzle.


Thank you for your indulgence,

BassCliff
 
BassCliff said:
Hi,

Is it true that you need to use a longer barreled pistol (5" or 6") to really take advantage of the increased velocity/accuracy of +P ammo? I seem to recall reading that in 4" or shorter barrels there's just not enough length to let the charge burn completely and build up to full pressure before the bullet exits the muzzle.


Thank you for your indulgence,

BassCliff
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Pretty much, yes. While you will still see an increase in velocity over standard pressure in short barrels, it will be not as dramatic as the increase would be in a longer barrel.
 
gwchitty said:
Can the Springfield 1911 45ACP pistols all handle +P and +P+ ammo. without damage to the gun.
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There's no .45+P+ ammo out there, at least not from reputable makers. So I’d avoid it.

But, yes, it will handle +P just fine; if you shoot a LOT of it—like thousands of rounds—you'll likely want to use a heavier recoil spring (and possibly stronger magazine springs, as well).
 
BassCliff said:
Hi,

Is it true that you need to use a longer barreled pistol (5" or 6") to really take advantage of the increased velocity/accuracy of +P ammo? I seem to recall reading that in 4" or shorter barrels there's just not enough length to let the charge burn completely and build up to full pressure before the bullet exits the muzzle.


Thank you for your indulgence,

BassCliff
Click to expand...
With the faster burn rate powders it will burn more of the powders in shorter barrels and still be useful in the 6". In rifles using faster/fastest burn rate may not have enough GAS VOLUME for the longer barrels. Revolvers (if a too fast of powder is used) with (larger bore and case capacity) can produce a squib depending on barrel length.
 
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