ammunition demystified
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Ammunition Demystifier – Overview

Ammunition – a word filled with mystery. When I began my journey into firearms, this subject and the overwhelming confusion that it created was almost enough to stop me in my tracks! I am one of those people that just dives in and consumes information relentlessly until I capture from it what I need, and I was beyond confused.

What I have come to understand is that it IS confusing! As a woman, I am not incapable, in any sense of the word, of figuring it out, (which I thought when I began researching ammunition!). However, I am practical. I want to know what I need to know and what it means for me, for my firearms and for my safety. I will try here to demystify and bring into clarity, the basics of what you need to know in regard to defensive ammunition, .380, 9mm, .38 Special, .357 Magnum, .40, .45 calibers.

ammunition demystifier

Let’s start with some basics


Ammunition: the projectiles with their fuses, propelling charges, or primers fired from firearms


The basic components of ammunition are the case, primer, powder, and projectile(s). Shotshells have an additional component called wad.

  • Case: The container that holds all the other ammunition components together. Typically made of brass, steel, copper, paper, or plastic.
  • Primer: An explosive chemical compound that ignites the gunpowder when struck by a firing pin. The primer is either in the rim of the case (rimfire) or in the center of the base of the case (centerfire).
  • Gunpowder: A chemical mixture that burns very rapidly and converts to an expanding gas when ignited. Modern smokeless powder will burn slowly when ignited in the open (outside of the case). Black powder is less stable and can be explosive when ignited in the open.
  • Projectile: The object(s) expelled from the barrel. A bullet is a lead projectile that fires through a rifle or handgun barrel. A slug is a lead projectile fired through a shotgun barrel. Shot is a group of lead, steel, tungsten, or bismuth pellets fired through a shotgun barrel.
  • Wad: A seal made of paper or plastic separating the powder from the slug or shot in a shotshell. The wad prevents gas from escaping through the shot and holds the shot together as it passes through the barrel.


Round or Cartridge: The correct and accurate name(s) for the “entire package”. It is not accurate to use the word bullet, as the bullet is one of the multiple components.

Bullet: The bullet is actually just the pointed top or tip that you typically think of when you picture a round. A shotgun round does not have an actual “bullet” inside. It has either buckshot, a lot of little round pieces or a “slug” which is shaped like a bullet.

Caliber: 1) The diameter of a bullet or other projectile, 2) the diameter of a bore of a firearm usually expressed in hundredths or thousandths of an inch and typically written as a decimal fraction, i.e. .380 caliber, .45 caliber, sometimes in the metric scale i.e.. 9mm. It is important to performance that a bullet should closely match the diameter of a barrel to ensure a good seal.

Gauge: The term “gauge” describes the bore diameter of a shotgun, but unlike “caliber” used for handguns and rifles, the larger the number, the smaller the bore.

Centerfire Ammunition: Ammunition in which the primer is located in a small cup in the bottom center of the case.

Rimfire Ammunition: Ammunition in which the primer is located in the bottom rim of the case. Typically, rimfire rounds are smaller calibers than centerfire rounds.

Hollowpoint: A metal jacketed cartridge design with a concavity in its nose to increase expansion on its penetration of a solid target. Some hollow-points are also designed to fragment as they expand. They are least likely to over-penetrate the target and harm an innocent bystander. Commonly used for self-defense

Softpoint: A metal jacketed cartridge design in which the nose of the core of the bullet is exposed to ensure the expansion of the bullet upon impact. Often abbreviated “JSP” or “SP.” They expand more slowly than a Hollow Point bullet. Shooters use these when they need deeper penetration and expansion.

+P or +P+ Ammunition

“Plus P” or “Plus P Plus” means that the cartridge is loaded with a higher pressure than standard ammunition. This gives your round more firing power and a greater impact on your target. You can see whether or not your ammo is +P or +P+ on the cartridge box, sometimes manufacture’s stamp this on the base of the cartridge. +P or +P+ cartridges are usually center-fire cartridges.


Grain is the actual weight measurement of the bullet component of a cartridge, not the entire cartridge. The more it weighs, the more grain it has. Standard weight for .45 ACP ball ammunition (full metal jacket – FMJ) is 230 grain. The standard for 9mm is around 115 grain.

Note: There are many inconsistencies in ammunition manufacturing so this number does not always reflect the actual diameter of the bullet and in some cases, manufacturer’s use the metric scale. In some cases, ammunition has a second number that represent length of the bullet. Letters (abbreviations or words) will then follow to complete the name of the cartridge. This entire “name” is important and you will need to know the entire description, including the letters.A

Ammunition Alphabet Soup

Yes, sometimes letters are added to the name to differentiate and describe rounds. These letters describe how the round is “packaged”. Every minute detail of a round effects how it performs. Performance of the round depends on the package. I did tell you it was complicated but not too complicated. I promise you will get it and will be able to approach a shelf of ammunition with confidence!

What Is FMJ?

FMJ is “Full Metal Jacket” and is used to describe rounds that are entirely encased (except for the bullet base, typically) in a metal jacket. Usually, copper alloy called gilding metal. FMJ rounds are standard and sometimes we refer to them as “ball”.  These rounds are designed with little to no expansion in mind. Which means that the bullet will maintain its circumference during and after penetrating the target. They are comparatively inexpensive, feed well and give good penetration in most materials.

What Is JSP?

AmmunitionJSP is “Jacketed Soft Point” and describes rounds that are encased in a metal jacket, again, usually a copper alloy called gilding metal, but leave the soft lead core exposed at the tip of the bullet. The soft nose deforms upon striking dense mediums, and these rounds expand rapidly at the nose and mushroom. This ensures that the center of gravity stays in front, and causing the bullet to continue traveling forward through the target. The larger frontal surface area causes more tissue disruption compared to most non-expanding bullets.

What Is JHP?

JHP is “Jacketed Hollow Point” and is used to describe rounds that are encased in a metal jacket, usually copper alloy called gilding metal, but have a small cavity in the nose along with a round opening in the jacket in the nose. JHP rounds expand and have faster “mushrooming” effects because the hollow point’s high-pressure material filling. When the bullet impacts the jackets peels back and creates a projectile that looks like a “mushroom”.




Let’s look at the anatomy of a round and what happens when it is fired. Killeen Bishop describes it in her article “Ammunition 101.”

“Looking at a cartridge from top to bottom, your first layer is the bullet. That’s what leaves the gun towards your target when you pull the trigger (assuming all goes well). The next layer is your powder charge. This is the part that the next layer of the bullet quickly ignites. The very bottom of your cartridge, usually the round shape at the base, is your primer. Primers ignite by striking the outside of that round shape or right on the inside of the round base, depending on whether or not it’s rim-fire or center-fire ammo.

What happens when you fire a gun is that the firing pin inside the gun hits the rim or centerfire. This causes an ignition of the powder inside the casing, which causes the bullet to propel forward towards your target and the casing to expel out the ejection port. This is how the casings end up landing all around, and sometimes even down your shirt. Since the casings have housed the fiery dance between the primer and the powder, they are inevitably hot, thus, you don’t want them to land down the front of your shirt and nest. 😉 Don’t worry ladies. I’ve even seen some men do the “hot casing dance”, too. It does happen and for the most part, you don’t have any control over them with the exception of what kind of clothing, hat, and eye protection you wear to inhibit the rogue piece of hot brass.”

Why does Understanding Ammunition Matter?

Using the wrong ammunition in your firearm is extremely dangerous. You must know the proper ammunition for your firearm. The owners manual that comes with your firearm will tell you exactly which ammunition is safe for your firearm to shoot and many manufacturers make the manuals available online as well. The caliber is stamped on the barrel of your gun.  Check the stamp on the bottom of the round to verify the caliber of our ammunition. You will also find the caliber noted on the ammunition box.


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3 thoughts on “Ammunition Demystifier – Overview

  1. Daniel Gilliam says:

    One thing I would recommend, in the discussion about higher powered ammunition (+P and +P+), is to add in that manufacturers recommendations and the users manuals need to be consulted to ensure that the handgunds are capable of handling those rounds. Most modern pistols can handle +P, but not all, and none of them allow +P+ without voiding the warranty (that I have ever heard of). In addition, when using these rounds, all of the recommendations are to use them sparingly because of increased wear and tear on the handguns. Just something I thought I should throw out there.

  2. Shannon Travers says:

    Good information for a new gun owner. Personal defense ammo explained as to why it’s defense ammo and what’s target ammo and why. I’m a .38 Special owner and was very pleased on the explanation of .38 Spc and what +P is. I now know what I need to purchase to permanently stop the uninvited guest if the situation ever arises.

  3. Tyler Johnson says:

    That’s good to know that full metal jacket bullets would be the standard for 9mm guns. I am thinking about getting a gun to do some target practice with, and that sounds like the best ammo to chose. I’ll have to make sure that I look for full metal jacketed bullets if I decide to get a gun.

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