Reader Randall writes:
While I’m not exactly a newbie when it comes to *using* firearms, I am a newbie gun *owner*. And now that I’m in the position of purchasing ammo, I’m finding things to be rather confusing when sorting out all there is to be had. I have Nick’s “Getting Started with Firearms” Kindle book, but it doesn’t really address the topic. How ’bout an article for us newbie-types explaining what’s +P and +P+ and all those others?
Good question. This area of ammunition, the +P and +P+ stuff, can get a little confusing and a tad dangerous . . .
When a gun goes off, the powder inside the cartridge burns and creates super-hot expanding gasses. Those gasses eventually push the bullet down the barrel, as that’s the path of least resistance for the gasses to escape. But since multiple manufacturers make ammunition marked with the same caliber designation, there needed to be a way to standardize the characteristics of each caliber so that gun makers and ammo makers could make products that work perfectly together and won’t blow up.
The good people at SAAMI (the Sporting Arms and Ammunition Manufacturers’ Institute) publish the official specifications for every cartridge. They dictate everything from the dimensions of the cartridge to the maximum pressure that the cartridge should produce. That keeps everyone on the same page when they make guns and ammo.
That second part, the maximum pressure bit, is extremely important. Gun makers use that number to figure out how thick the gun’s chamber and barrel should be to safely contain that pressure round after round. The guns are tested with a high pressure “proof load,” which is designed to produce a much, much higher pressure in the barrel than the listed maximum chamber pressure according to SAAMI.
The proof load replicates the “worst case scenario” and ensures that the gun can safely contain such a round and still operate, but guns are designed to function mainly on the lower standard pressure rounds. The gun will work using proof loads, but the parts will wear out extremely fast and the gun will quickly become unusable and unsafe.
While standard pressure ammunition is nice, some people (especially those using it in self defense firearms) believed that they needed more power. To illustrate the type of person who believes that .45 ACP isn’t enough and needs more oomph, I present an orangutan yelling “POWER!!!!”
So that’s the impetus behind the +P and +P+ stuff, people wanting to get more velocity or a heavier bullet in a traditional and standardized cartridge than the specs would allow without changing the dimensions. Unfortunately, the result of those changes is that the chamber pressure of the rounds exceed the maximum pressure specifications for normal, factory ammunition.
+P, pronounced “plus pee,” is a recognized “overpressure” load for ammunition that SAAMI officially blesses. The institute publishes the maximum allowable pressures for these loads as well as the standard cartridges, allowing firearms manufacturers to produce guns capable of safely handling round after round of the hot stuff without damaging the gun. +P loadings are offered for the standard self defense rounds of 9mm Luger, .45 ACP and .38 Special among others.
Since +P cartridges are typically only 10% above the normal pressure of a cartridge they will work in any properly maintained gun (the proof round is still a much higher pressure), but they will wear it out sooner and increase the chances that the gun will suffer a “structural failure.” Which is code for “blow up in your hand.” So the common advice is to not use +P as range / practice ammo.
.38 Super is the exception to the rule. The +P loading for .38 Auto, dubbed “.38 super,” is a standard competition load used in USPSA and 3-gun competitions. The ammunition is loaded much, MUCH hotter than the typical +10% and almost becomes its own caliber. This is the only +P loading that I would stay away from for novice shooters.
+P+ or “plus pee plus,” is a loading above the already over-loaded +P designation. This is for people who don’t think that +P is enough “stopping power” and want even more. But this is the point at which SAAMI draws the line. There are no standards for +P+ ammunition, it is simply “more” than +P.
Since the load is supposed to be still below the pressure of the proof cartridge, it should work fine once or twice in your gun. But prolonged usage will wear out your gun faster than +P. And the fact that there really is no official specification for +P+ means that there’s no way to really know what you’re getting. At that point, you’re putting your faith in your brand of ammo manufacturer to not overpressure the round too much, and your gun manufacturer to have designed the gun well.
Personally, I’m of the opinion that “stopping power” is a myth. The real thing you should be concerned about is shot placement, not how fast or how heavy your bullets are. So long as they can pierce someone’s chest they’re good enough. That’s why I carry normal factory ammunition in my gun. But for some people, their belief in the “stopping power” myth is strong enough that they need to risk permanent damage to their guns and the possibility of a “catastrophic failure” to squeeze those last few foot pounds out of their guns.
My advice: stay away from all the +P stuff.