What is +P Ammo?
+P ammunition, also called overpressure ammunition, is ammo that is loaded to achieve a higher internal pressure than a standard round of the same caliber. This change in pressure means that +P ammo offers some ballistic advantages over standard ammo, but those advantages come with some costs, too, and we don’t just mean financial.
In this guide, we’ll go into more detail about what (and why) +P ammo is, its advantages and disadvantages, and why you might want to opt for +P or standard ammo.
What is +P Ammunition?
+P ammunition is loaded with extra powder compared to a standard round, allowing it to achieve higher internal pressures. In fact, the Sporting Arms and Ammunition Manufacturers Institute (SAAMI), the organization that sets standards for commercial ammunition manufacturing in the United States, has separate maximum pressure standards for +P ammo and standard rounds.
Most ammunition that has been developed in +P loads are older rounds, from the late 19th and early 20th century, that have maintained popularity into modern times. The sort of pressure levels that +P rounds have weren’t possible when these calibers were first developed.
Modern firearm and ammunition technology, however, has made higher pressure levels possible, hence the development of +P ammo. Improved powder is the biggest contributor. You could only increase pressure by adding more powder, so pressure was limited by case capacity. With improved powder, manufacturers can get higher pressures from the same capacity. Improvements in metallurgy are also an important factor though, since older guns in these calibers often would not be strong enough to handle the higher pressures achieved by +P ammo anyway.
Generally, SAAMI specifications for the maximum average pressure of +P ammo usually have about a 10 percent increase compared to standard rounds, but it varies depending on the caliber. The standard maximum pressure for .38 Special, for example, is 17,500 PSI and the .38 Special +P max pressure is 20,000, representing a 14.29% increase. .380 ACP has a whopping 37.74% increase. 9mm and .45 ACP are more typical examples. The former has an increase of pressure of exactly 10% while the latter has a 9.52% increase in pressure.
But what does the increased pressure mean for you?
Pros and Cons of Using +P Ammunition
Well, higher pressure means two things: higher speed and higher energy compared to a standard round of the same bullet weight. Those can be either good or bad. On the good side, those things mean a flatter trajectory. That’s not necessarily a guarantee of better accuracy, but it does make aiming easier. It also means the bullet hits the target harder than a bullet of the same weight from a standard round. That’s irrelevant for target shooting, but it’s a big advantage for defensive ammo. A +P round will, at least in theory, do a lot more damage to a would-be attacker than a standard load.Higher velocity means deeper penetration, more energy transferred to the target, better expansion of hollow point and soft point projectiles, and all of that means much better performance when in a self-defense situation or hunting. +P rounds are especially useful for guns with a shorter barrel length, like snub-nosed revolvers, since shorter-barreled weapons tend to achieve lower muzzle velocity. This is why you’ll see a lot of +P .38 Special ammo out there, as this is the most common revolver chambering.
On the other side of things, increased energy also means increased recoil. That means more muzzle flip, so slower follow-up shots since it takes more time to re-aim at your target. It’s not necessarily a big difference, but in a defensive situation, every fraction of a second counts. Increased recoil also just makes a gun less comfortable to shoot, so extended training sessions won’t be as easy as you’re used to. Fortunately, there are things that you can do to help minimize muzzle flip and generally control recoil. A ported barrel or compensator can make a huge difference when shooting high-pressure ammo and can tame those high recoil impulses even when rapid firing.
The other thing to consider when firing +P ammo is the extra wear and tear those higher pressures put on the gun itself. Whether you shoot a semi-auto pistol or a revolver, the increased chamber pressure of +P ammunition puts greater wear on your gun. In the case of semi-autos, it increases the strain on those little moving parts, while for a revolver, the pressure is on the cylinder. In either case, the faster bullet, and increased friction as a result, can wear down the rifling inside the barrel faster as well.
It’s also important to remember safety. Just because a gun is rated for standard ammunition doesn’t mean it’s rated for +P ammunition. Fortunately, most modern guns can handle +P ammo, but you should still always check to make sure. Typically, manufacturers will let you know, prominently, if a gun is rated for +P ammo in the manual that came with the gun, which should be available online if you’ve misplaced yours or bought your gun secondhand and never had one to begin with.
Finally, +P ammo is loaded to higher pressures with typically finer-grained powder, which requires more processing. Simple economics means that this ammo is then going to be more expensive than standard pressure ammo. This is compounded by the fact that a lot of +P ammo is intended for hunting or defense, which of course means some sort of jacketed or solid-copper projectile with a hollow tip designed for expansion. All of which means more expensive projectiles and thus a higher cost per round.
How to Choose Between +P and Standard Ammunition
There’s no hard and fast rule about when you need +P or standard ammo, but there are some general guidelines you can follow that can make the decision easier, and some things to keep in mind that may sway you one way or the other.
The biggest consideration is a simple question: “Do you need the extra velocity?” Often the answer is going to be just as simple: “Nope!”
For target shooting and general plinking, there’s no real need for the extra velocity and the resulting extra wear and tear on your gun, or the extra expense of the rounds. You’re making your job harder when it comes to shooting, and you’re paying more to put a hole in paper or a tin can. The exception would be if you’re training for a situation in which you’re using +P ammo, such as self-defense training. Running your drills with ammo that is as close as is reasonably possible to what you’ll be carrying for defense is an important part of being prepared.
That said, if you’re training a lot, especially if you’re doing competition or an involved shooting class, then running high-pressure ammo may not be viable on the budget side of things. Make no mistake, +P ammo is definitely more expensive, and you do get what you pay for. In this case, going with standard ammo is probably the better choice unless money truly is no object. For most people, starting and ending each training session with a magazine or even just a few rounds of high-pressure ammo is enough to stay accustomed to the recoil. Remember, the recoil isn’t going to be that much higher for +P ammo, so it’s not like you’re going to be missing out on much by training with standard pressure stuff for the majority of the time.
Now, when it comes time to actually carry ammo that is going to be potentially used for defense, or for hunting, then it’s time to step up to the +P or even +P+ stuff for the extra terminal performance. There’s no two ways about it, more velocity is just better when it comes to creating wound channels in soft tissue.
Higher velocity +P ammo does a better job of passing through bone and heavy clothing, and even hard barriers like a car windshield. The extra recoil isn’t really a concern, especially if you’ve been training appropriately, and the extra performance can be a literal lifesaver.
It is worth noting that +P ammunition is rarely used by police agencies or other law enforcement agencies. You can certainly rely on standard loads for personal protection, especially if you’re using hollow points. However, +P ammo does offer a significant improvement in terminal ballistics compared to standard rounds.
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In summary, +P ammo achieves higher pressures than standard rounds of the same caliber, generally by about 10%. This higher pressure results in a flatter trajectory and more power, making +P ammo particularly well-suited for hunting and defensive purposes.
However, that comes at the cost of increased recoil, as well as increased wear and tear on your guns. +P ammo also can’t be used with all firearms, so you should always check to make sure your gun is safe to use with +P ammo before loading it in. Finally, +P ammo does have a higher cost than standard rounds.