Decoding The Ammo Box: A Primer For New Gun Owners

Decoding what’s on the end of the ammo box: a primer for new gun owners

So you got a new gun, and now you need some ammunition. Making a choice based on the acronyms on the end of the ammo box—typically what’s visible when shopping for ammo at your local hardware or big box store—can be daunting. Knowing what those acronyms mean can help you be a shopper who spends their hard-earned money on exactly the ammo you need.

Here’s a Rosetta Stone, of sorts, for the most common ammo terms and abbreviations:

Jacket and bullet types

HP or JHP = Hollow Point or Jacketed Hollow Point. These rounds are generally a bit more expensive, and designed for defensive and hunting use. A hollow point is made to open up and “mushroom” or fracture after a short distance of penetration, and is usually made to expend all its ballistic energy within around 12 inches of impact.

The “jacketed” term indicates the bullet itself, which may be lead or a combination of metals, is coated with a layer of metal, usually copper. This improves feeding in semi-autos and controls expansion of the hollow point.

Many gun carriers consider HP/JHP ammunition the responsible choice for self-defense, as it’s less likely to pass through an initial target and into another, innocent person. This is NEVER a guarantee in a real-life, dynamic situation. An example is an attack in which the best target area is something like a knee joint, if that’s all that’s visible or all that can responsibly be targeted.

mushroomed hollow point

The copper-jacketed .380 round (L) and solid copper .45 hollow point bullet (R) have blossomed to their full potential after hitting a solid target—a gel block in this case. Thanks to Double Tap Ammunition for the live fire test.

FMJ or TMJ = Full Metal Jacket or Total Metal Jacket. Most common and generally less expensive than HP, FMJ/TMJ ammunition has a usually copper coating over the entire bullet. This is the round of choice for most people for practice and plinking. In general, jacketing helps feeding consistency (read dependability) in semi-auto pistols and rifles.

SP, JSP, and Wadcutter = Soft Point, Jacketed Soft Point, and Wadcutter. These refer to bullets with exposed or only partially jacketed lead. These are most commonly seen in ammo intended for revolvers, such as 38 Special, 357 Magnum, and 45 Long Colt. Wadcutter ammunition is less common today, but is still considered a good choice for shorter-range match shooting as it’s highly accurate.

These are common ammunition types. There are variations on these themes, such as jacketed hollow points that have a small polymer plug inside the bullet (which is visible). There are HP rounds which are designed more for fragmentation than simple expansion. Lead-free and polymer-coated bullets are recent additions to the scene. Lead-free bullets are a boon for people who shoot indoors on a regular basis and want to minimize toxin exposure. Polymer bullet coating, like Federal’s Syntech, is gaining popularity for match shooters and is said to minimize recoil and keep guns cleaner and cooler.

Grain weight

Grain weight, which isn’t relevant to any modern measure except bullets, is also provided on the box end. Heavier bullets may, at first glance, seem a better choice for self-defense or hunting, as they generally achieve better penetration. However, heavier bullets also travel more slowly, which decreases overall impact. It comes down to a matter of personal preference.

Looking at a 9mm bullet from the rear (L) and side, the reason for the “full metal jacket” moniker is obvious.

Grain weight is far less important than reliability. Not every firearm cycles every round dependably. Grain weight, and while we’re discussing choices, cost, are not always reliable indicators of performance. It’s the interface of your firearm’s construction with that of the cartridge that counts. Practice with your defense or hunting round of choice before you need it.

Case types

Pistol ammunition is generally found with one of three casing types—brass, aluminum, or steel. The case is, physically, the biggest component of your ammunition and holds the primer, powder, and bullet in place. Case material can make a difference in the performance and/or longevity of your gun.
Generally, brass-cased ammunition is preferred. It’s also most widely recognized as acceptable by gun manufacturers.

Aluminum cases may or may not be okay by owner’s manual standards. In some market phases, aluminum-cased ammunition, usually found in FMJ, is more affordable. As of this writing and in my local area, aluminum-cased pistol ammunition is more expensive than some brands of brass-cased FMJ.

Steel-cased ammunition is not recommended for most firearms as it, unlike brass and aluminum, is the same or nearly the same hardness as the inside of your chamber, extractor, and feed ramp, if there is one. Steel cases can cause premature wear that, over time, negates the lower price of this ammo.

These are general guidelines, and there are good and bad exceptions. Though it’s not touted as a precision round, I’ve good results with both reliability and accuracy with both Federal and Blazer 115 grain aluminum cased ammo when used for 25-yard courses of fire with a pistol and a Glock-to-carbine conversion kit called the KPOS Scout. What performs well in, say, your Taurus Millennium pistol may not work so well in the same model that belongs to a friend. Testing a particular brand in your pistol is the only way to know without a doubt how it’ll perform.

+P and +P+

Ammunition with +P or +P+ designation is most often seen in revolver calibers like .38 Special (though is found on semi-auto pistols as well). This ammunition has a bigger powder charge in the case and is thought to deliver more “oomph” on target for defensive applications. A future article will delve more deeply into this sub-type. In the meantime, check the caliber rating stamped into your barrel or gun owner’s manual to see if it’s safe to use +P-rated ammo in your gun.

Brand confusion

Different companies may have different terms—and thus box-end abbreviations–for very similar products. For example, some companies use the letter “n,” as in “nose,” to signify the shape of the business end of the bullet. Such variables can trip up even experienced gun shop workers. If you’re unsure, ask to see the box, and read it, or search the company’s website. Most ammunition makers do an excellent job with online product descriptions.

So many box ends to interpret. Here’s help.

That little book can prevent headaches

The owner’s manual for your gun, which you can search for online if you don’t possess, is the best starting point for choosing ammunition. Some manufacturers recommend only American-made, brass-cased ammunition that is guaranteed to meet certain manufacturing standards. Some brands even deny warranty claims if ammunition other than what the manual recommends is used.

The KISS principle

This article covers the most basic components of ammo lingo. Like any new language, there are dozens of variables and application-specific terms that are best learned by doing.

Buyers should avoid getting caught up in spending a fortune on ammunition that’s touted as extra-special in any way–for accuracy, expansion, or the tactical trick of the season. Your best bet is to purchase something that’s reasonably priced and in accordance with the recommendations found in your owner’s manual. Some ammunition may cause malfunctions in your firearm on a consistent basis. So long as your life isn’t at stake, and assuming the malfunctions aren’t causing a safety issue, consider that ammunition your go-to for practicing malfunction clearing, an important aspect of shooter competence.

The biggest investment shouldn’t be in ammo, but in time spent practicing the fundamentals of marksmanship. Happy and safe shooting!

About Eve Flanigan

Eve Flanigan is a defensive shooting and lifestyle student, practitioner, and instructor based in the American Southwest. She is a lifelong recreational rifle shooter who began carrying concealed in 2004, which evolved into an interest in defensive handgun training and competing. Flanigan holds NRA Instructor certifications in pistol, rifle, and personal protection in the home. She is licensed to instruct New Mexico’s intensive Concealed Carry course, and regularly designs, conducts, and co-teaches classes on concealed carry, introduction to pistol, defensive pistol, basic rifle, last-ditch medical, and use of force for civilian students. Flanigan enjoys competing in run-and-gun biathlons that include carbine and pistol.


  1. Shelia Roberts on October 31, 2020 at 10:52 am

    Thanks for the info. I would love to see a chart with lots of ammo box codes like LHP, HP, etc. I have put the codes that I have found so far in my phone so that when I shop for ammo, I know what I’m getting. Thanks.

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