p ammunition

All About Plus P Ammo and Using It

When it comes to ammunition for defense purposes, one of the most constant recommendations is to use +P ammo. There is some discussion about whether plus P ammo is necessary or advisable to use in some firearms, which may give some people pause about whether use is prudent.

This kind of ammunition is very popular among both police but also concealed carriers, as it is very popular as self-defense ammo.

Plus P Means Overpressure

Plus P

"Plus P" ammunition means "overpressure." This involves a little bit of basic science.

So, how a bullet works is fairly simple. The hammer/striker/firing pin sets off a primer, which is a tiny explosive charge, which in turn ignites a larger charge.

When the main powder charge (called "propellant") is ignited, this creates a small explosion inside the cartridge. This creates a huge amount of pressure inside a small space. Pressure in any enclosed space looks for any way out it can find, so the pressure inside the enclosed space can reach the same pressure as the ambient pressure outside it. (Nature abhorring them vacuums.) This causes the bullet to fly out of the barrel toward.

What does this overpressure do? Increases in pressure result in increased velocity. Ergo, the higher the pressure, the faster a bullet flies.

A lighter bullet can help as well, which is why a 115-grain 9mm bullet is faster than a 147-grain bullet, and this is also why many +P loads do and don't employ lighter projectiles. (Either to maximize velocity or get more velocity from a heavier projectile.) A similar concept is employed by necked-down rifle cartridges; a normal load for a larger cartridge can produce a very fast, flat-shooting bullet when the case is necked down to fit a smaller projectile, such as the .270 Winchester, which is made by necking down a .30-03.

The short version is more gunpowder more pressure, making the bullet fly faster.

Using Plus P

using plus p ammunition

That said, each specific cartridge - and more importantly, the firearms that fire them - are designed to tolerate specific pressure levels, which plus P ammunition can exceed.

The Sporting Arms and Ammunition Manufacturer's Institute, or SAAMI, maintains weights and measures, if you will, for guns and bullets. That includes pressure ratings for cartridges. Basically, they set the bar for what ammunition is +P and what ammunition isn't +P.

For instance, SAAMI rates the 9x19 Parabellum (good old 9mm) maximum chamber pressure at 35,001 PSI, and 9mm +P at 38,500 psi. Anything over +P ratings is +P+, which is a whole other can of worms.

Why is this important? Higher chamber pressures exert greater wear and tear on the chamber and any moving parts. (The pressures actually stretch the metal.) Semi-automatic pistols can even fail to cycle with overpressure ammunition, if not suffer catastrophic failures in some cases. Even revolvers, including the large magnum revolvers, are susceptible to damage as well, unless - like some Ruger revolvers - they are engineered for higher-than-normal chamber pressures.

Granted, shooting .38 Special +P in a .357 Magnum is perfectly fine, as .38 Special +P generates far less chamber pressure than .357 Magnum.

Depending on your make and model of pistol, +P ammunition may be recommended only in limited servings, may be completely fine, or the manufacturer may strenuously advise that it never be used. Heed these warnings, as the people who engineered the gun to begin with know better than you do.

Is +P Ammunition Worth It?

is plus p ammunition worth it

Is it worth buying +P ammunition? Is it really that much better than a JHP load within normal pressures?

There's a certain amount of evidence to suggest that using Plus P ammo is worth it. Many police departments nationwide have been relying on +P and +P+ ammunition for years to bring their officers back alive, so there is that track record. After all, the best way to ensure that a hollow point expands reliably is to put a few more grains of powder behind it.

To be fair, expanding hollow point ammunition is not what it once was. In past decades, +P loads actually WERE necessary because standard pressure hollow points were found to not expand reliably when used by police. In particular, 9mm was notorious for it, but some hot loads - such as SuperVel's and CorBon's 115-grain +P and 115-grain +P+ JHP rounds - were found to work very reliably. The same was also true of 158-grain .38 Special ammunition; it was found that 158-grain +P loads were more reliable than 158-grain semi wad cutters loaded to standard pressure.

In the fullness of time, ammunition makers improved their products. By the 1990s, standard-pressure loads of Speer Gold Dot, Winchester Ranger, Remington Golden Sabre and others performed just as well as their overpressure variants after years of development.

It's also worth pointing out that handgun wounds are not actually fatal very often. Numbers vary, but more than 80 percent of people wounded with a handgun survive if they aren't killed right away. Adding another hundred feet per second...isn't really going to do much. It doesn't matter if you size up to .45 ACP or 10mm or even .44 Magnum. It's really only long guns that have serious wounding potential. Ultimately, what stops most people that are shot by police or by armed citizens is the sheer shock of being shot.

There is ample evidence that standard pressure rounds of good design are just as reliable as Plus P ammunition in the same caliber. Load selection is important of course, but it's not as important as some people insist that it is.

Sam Hoober  

About The Author

Born in southeastern Washington State, Sam Hoober graduated in 2011 from Eastern Washington University. He resides in the great Inland Northwest, with his wife and child. His varied interests and hobbies include camping, fishing, hunting, and spending time at the gun range as often as possible.

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