This topic confuses a lot of shooters. That is not surprising because there are so many different types of ammunition with many different names and abbreviations.

Over the years, different manufacturers have designed and marketed different calibers of ammunition. Some calibers have failed in the market and some have succeeded. The successful ones have become standards. Examples of well-established standard types of ammunition that you have probably heard of are: .22 LR (Long Rifle), 38 Special, and 9mm. Once an ammunition standard is established, many different gun manufacturers will design guns to shoot that standard ammunition caliber. Usually, a single gun will shoot a single “caliber” of ammunition.

Once you have figured out what caliber of ammunition you should use, there are other variations the manufacturers can add. For example, they can insert heavier or lighter bullets into the cartridge. Or, they can use a different type of bullet in the cartridge (hollow point or full metal jacket would be examples of different types of bullets).

So in general, when you are trying to figure out what type of ammunition you should shoot in your gun, you should ask four questions;

  • What caliber? .22LR? .380 ACP? .40 SW? 9mm?
  • What pressurization? Factory? +P? +P+?
  • What bullet weight? 115 grains? 180 grains?
  • What style bullet? Hollow point? Full Metal Jacket?

We’ll teach you how to answer those questions in this section. But first, a bit about how ammunition works.

The Basics

Parts of an Ammunition Cartridge

The four parts of a cartridge - rimfire and centerfire ammunition

The four parts of a cartridge – rimfire and centerfire ammunition

Handgun ammunition has four parts:

  • The bullet. The bullet is a lead or metallic slug in the top of the cartridge. The bullet leaves the gun at high velocity.
  • The casing The casing holds the primer, gunpowder and bullet together before the gun is discharged. Unlike the bullet, the casing does NOT exit the gun through the barrel.
  • The gunpowder. The gases from the burning gunpowder expand quickly and propel the bullet out of the casing and through the barrel of the gun.
  • The primer is a small, very explosive substance at the bottom of the cartridge. It is pressure sensitive. Thus, the firing sequence begins when the firing pin in the gun hits the primer and ignites it.

Note, it is not correct to call a cartridge a “bullet.” The bullet is just the part of the cartridge that is shot from the barrel of the gun. The correct term for the entire piece of ammunition is “round” or “cartridge.”

Centerfire and Rimfire Ammunition

There are two types of handgun ammunition, centerfire and rimfire. The names refer to where the primer for the cartridge is located—in a rimfire, the primer is in the rim while in a centerfire, the primer is in the center of the base of the cartridge.

How Ammunition Fires

When a cartridge is fired, the following sequence of steps take place:

  1. The trigger is pulled;
  2. That causes the gun’s firing pin to hit the primer in the cartridge.
  3. The primer is pressure sensitive. So it ignites, causing the gunpowder to burn.
  4. The gunpowder burns rapidly after it ignites. The expanding gases from the gunpowder propel the bullet out of the gun, leaving the casing behind in the gun.

Ammunition Caliber

“Caliber” refers to the approximate internal diameter of the barrel or the diameter of the cartridge used in it. It is measured either in inches or in millimeters. Examples of calibers measured in inches are .38 Special and .45 caliber. Examples of calibers measured in millimeters are 9mm Luger (a common self-defense round) and 10mm (used by the FBI).

The larger the caliber, the bigger in diameter the ammunition (and the bigger the diameter of the bore of the gun that shoots it). In ascending order of diameter, here are some common handgun calibers:

Small Calibers

  • .22 LR (Revolver or Semi-Automatic)
  • .25 Caliber (Semi-Automatic)
  • .32 Caliber (Revolver)

Medium Calibers

  • .357 Magnum (Revolver)
  • .380 ACP (“James Bond”, Semi-Automatic)
  • .38 Special (Revolver)
  • 9mm Luger (Semi-Automatic)
  • .40 Caliber (Semi-Automatic)
  • .45 Caliber (Semi-Automatic)

Large Calibers

  • .44 Magnum (“Dirty Harry”, Revolver)
  • .454 Casull (Semi-Automatic)

The medium caliber rounds are the most common self-defense rounds. The smaller calibers are often thought to lack “stopping power.” The larger calibers often require guns that are too large or powerful for most people to carry for self-defense.

The following picture gives you a sense of the relative sizes of different calibers of handgun ammunition.

Different calibers of handgun ammunition

Different calibers of handgun ammunition

From left to right: (1) Shotgun shell; (2) AA Battery; (3) .454 Casull;  (4) .45 Winchester Magnum; (5) .44 Remington Magnum; (6) .357 Magnum; (7) .38 Special; (8) .45 ACP; (9) .38 Super; (10) 9mm Luger; (11) .32 ACP; and (12) .22 LR.[1]

For a nice visual demonstration of ammunition calibers, see:

Matching Ammunition to a Handgun

There is one absolute rule for using ammunition. MAKE SURE YOU HAVE THE RIGHT CALIBER AMMUNITION FOR YOUR GUN BEFORE YOU SHOOT. Here is how to do that.

You can find out what ammunition your gun will shoot safely in two different ways:

  1. Look in the owner’s manual that came with your gun.
  2. Look on the gun. It is stamped into the metal somewhere. For a revolver, the caliber is almost always stamped on the barrel. For a semi-automatic, it is usually stamped near the chamber.  The Bureau of Alcohol, Tobacco and Firearms requires all manufacturers to stamp the caliber on guns sold in the USA. [27 CFR § 478.92(a)(1)]. Here is an example of what one of those stamps looks like—this gun shoots .22 LR ammunition. You can see that stamped on the gun.
A semi-automatic pistol's caliber stamp

A semi-automatic pistol’s caliber stamp

You can find out what caliber a box of ammunition contains in two ways[2]:

  • Look on the base of the ammunition (the flat part where the primer is). The caliber is almost always stamped on the ammunition:
'357 Mag' stamped on the base of a cartridge

‘357 Mag’ stamped on the base of a cartridge

  • Look on the box the ammunition came in. The caliber of the ammunition and the gun should match.

You need to match more than just the numeric caliber. All the numeric caliber tells you is how big around the cartridge is. It doesn’t necessarily tell you how long the cartridge is, how powerful the powder load is, and so forth. So look for additional information about caliber. For example, “.357 Magnum” is different than “.357 SIG”—one shoots in revolvers and one shoots in semi-automatics.

The rule is, if you are not certain the ammunition is right for your gun, don’t shoot it. If all else fails, you can call the manufacturer or take it into a shooting range or somewhere that sells ammunition and ask.

Here are a few special rules about matching ammunition to a handgun:

  1. 9mm Ammunition. There are many different names for standard 9mm ammunition that mean the same thing. The following terms refer to the same caliber of ammunition and are used to refer to the most common 9mm ammunition used in the United States: 9mm Luger, 9mm Parabellum, 9mm Para, 9mm NATO, and 9×19. On the other hand, although the following calibers have “9mm” in the name, they refer to entirely different calibers and should not be shot in a gun labeled, for example, “9mm Luger.” They are: 9mm Short, 9mm Kurtz, 9mm Markov, 9mm Corto, 9×18, 9mm Long. This is not an exhaustive list. There are many varieties of 9mm ammunition around the world.
  1. .380 Ammunition is usually referred to as .380 ACP. But sometimes you will see it referred to as 9mm Short, 9mm Kurtz, or 9mm Corto.
  2. .38 Special Ammunition. You can shoot .38 Special ammunition in a .357 Magnum handgun. The reverse is not true. A nice video demonstrating the difference between .38 Special and .357 Magnum handguns and ammunition may be found here:   

  1. .22 Caliber Ammunition. The following terms refer to DIFFERENT calibers of ammunition: “.22 Short”, “.22 LR” (or “.22 Long Rifle”), and “.22 Magnum.” Don’t shoot one of them in a gun designed for another caliber.

This is not an exhaustive list of the special rules for identifying ammunition, just the ones that raise the most questions in our classes. If you are not certain, don’t shoot it.

Ammunition Pressurization

You may see the terms, “+P” and “+P+” used in connection with ammunition. These refer to cartridges loaded with gunpower that produces a higher pressure on discharge than a standard cartridge of that caliber. So a 9mm Luger +P round has more punch than a standard 9mm Luger cartridge.

The rule for non-standard pressurizations: DO NOT SHOOT +P or +P+ ammunition unless you know FOR CERTAIN your handgun is designed for it. You can DESTROY your gun and injure yourself or others.

Although many different calibers have +P ammunition manufactured for them, this is a particular concern for .38 Special guns. There is considerable evidence that standard-pressure, .38 Special JHP ammunition will not expand on impact when shot out of the modern .38’s designed for concealed carry, which have short barrels for concealment. On the other hand, some of the .38 Special +P ammunition appears to expand well when shot from these same guns.

Accordingly, if you are buying a .38 Special gun, you should try to find one that is expressly designed to handle +P ammunition. If you have an older .38 Special, it is likely not to handle +P pressures well and +P ammunition should not be shot from them. Again, makes sure your gun is designed for +P before you use +P in the gun.

Bullet Type

Regardless of caliber, there are different styles of bullets that can be put into a cartridge. As one example, for example, you can find Full Metal Jacket (FMJ) style bullets in many different calibers of ammunition.

Different types of bullets have different effects when they strike a target. Those effects will be discussed below.

The different bullet styles are often referred to by two or three letter abbreviations, like “FMJ” or “HP”. Some of the more common bullet style designations and abbreviations you will see are:

Hollow Point Bullets (JHP, SJHP, LHP and HP)

Common abbreviations for this type of bullet are “JHP” (Jacketed Hollow Point), “SJHP” (Semi-Jacketed Hollow Point), and “LHP” (Lead Hollow Point). The three bullet styles are shown below:[3]

A jacketed hollow-point bullet (JHP)

A jacketed hollow-point bullet (JHP)



A semi-jacketed hollow point bullet (SJHP)

A semi-jacketed hollow point bullet (SJHP)

A lead hollow point bullet (LHP)

A lead hollow point bullet (LHP)

All three have the hollow point in common. All three are primarily lead. What makes them different from each other are the jackets (or lack thereof) around the lead. The jacket is typically copper. Its purpose is to protect the barrel of the gun from lead fouling as the bullets travel through the barrel. In addition, the jacketing allows the bullet to withstand higher velocities.

The hollow point design causes the bullet to expand (or mushroom) rapidly when it hits soft tissue and therefore, to stop in soft-tissue targets. This has two effects: (1) more of the energy of the bullet is deposited in the intended target because of the mushrooming and the bullet is more likely to stop a perpetrator from doing what he is doing; and (2) the expansion makes it less likely the bullet will travel through the perpetrator and hit an innocent person behind the perpetrator. For these reasons, hollow point bullets are the most commonly used self-defense bullets in the United States.

Full Metal Jacket or Round Nose Bullets (“FMJ” or “RN”)

This bullet style is missing the hollow point—the tip of the bullet is rounded. It is typically jacketed. Unlike hollow points, it is not likely to expand in the target and is, therefore, more likely to pass entirely through the target with enough energy to endanger innocent persons behind the perpetrator. So this type of ammunition is normally used for target practice, not self-defense.[4]

A full metal jacket bullet (FMJ)

A full metal jacket bullet (FMJ)

Fragmenting or Frangible Bullets

Some bullets are designed to fragment quickly once they hit soft tissue or are pre-fragmented. This bullet style tends to penetrate very little but to leave a very large, shallow wound. It is also thought to be safer shooting in an enclosed environment like an airplane because it is less likely to penetrate walls. Examples are Glaser Safety Ammunition and V-Max bullets. The Glaser is pre-fragmented—like a little shotgun shell. An artist’s conception of the Glaser bullet is shown below.[5]


Artist's conception of Glaser safety ammunition

Artist’s conception of Glaser safety ammunition

Wadcutter Bullets (WC)

Wadcutter bullets have flat noses. They cut very clean holes in paper targets, making scoring easy. So they are used primarily for target practice. A wadcutter bullet looks like this.[6]


Lead wadcutter bullet

Lead wadcutter bullet

Soft Point Bullets (SP or JSP)

Soft point bullets are half-way between FMJ and JHP bullets. They have a soft, exposed lead tip but are partially jacketed on the sides of the bullet. The soft lead tip expands or mushrooms when it hits soft tissue, but does so more slowly than does a hollow point. Thus, the soft point penetrates more and expands more slowly than does a hollow point. Cartridges containing JSP and JHP bullets may be compared below.[7]

Jacketed soft paint (left) and jacketed hollow point (right)

Jacketed soft paint (left) and jacketed hollow point (right)

 Bullet Weights

Bullet weights are measured in grains—there are 15.4 grains in a gram—so a grain is a small unit of measurement.

Ammunition of the same caliber can have different weight bullet. For example, common bullet weights for .22 LR ammunition are 36 grains and 40 grains.

Heavier bullets move more slowly and have more recoil. In addition, they tend to retain their velocity for a further distance than do lighter bullets. On the other hand, lighter bullets move faster and have less recoil. But they lose their velocity faster than do heavier bullets.

You will find the weight of the bullet on the box the ammunition comes in. “Grains” is usually abbreviated “Gr.” As long as you have the right caliber of ammunition, you can usually shoot different grain weight bullets. Attempting to shoot a wrong grain weight may cause the gun to misfeed, but it will not damage the gun because of the grain weight.

Reloaded and Remanufactured Ammunition

After a cartridge has been discharged, the brass casing can be used to create another usable piece of ammunition or a “reload”.  Individuals can collect the brass casing and reload it or companies may do it.  When a company does it, it is referred to as “remanufactured” ammunition.

Both are less expensive and also probably less reliable than newly manufactured ammunition, although our experience has been that some remanufactured ammunition is very reliable. On the other hand, hand-reloaded ammunition is, in our opinion, a very dicey proposition unless you do the reloading yourself and you do it very well. You need to trust the person doing the reloads to be very careful and consistent in making the reloads. Buying hand-reloaded ammunition from someone you do not know and trust is, in our opinion, a bad idea. Bad things can happen to you and your gun. Here is a photo of a gun after a reload blew up in it.


Oops! Shot a reload in a 38 special

Oops! Shot a reload in a 38 special

Storing Ammunition

Store ammunition in a cool, dry place. It should be stored where unauthorized people can get to it and it should be stored separately from your firearms. Properly stored ammunition has an unknown but very long shelf-life—decades at least.

Disposing of Ammunition

Take it into a shooting range or a law enforcement office. They know how to properly dispose of it. Ammunition is a hazardous waste and should not be thrown in the trash or buried.

Ammunition Malfunctions

Ammunition is not perfect. Sometimes it malfunctions. This section describes the three types of ammunition malfunctions and what to do about them. The three types are: Hang-fire, misfire and squib load.


You pull the trigger. Nothing happens. This may be caused by a “hang-fire.” A hang-fire is a cartridge that does not go off right away. This is a dangerous condition because the round might still go off. If you are examining the gun or pointing the gun in an unsafe direction when that happens, damage to your gun and/or injury to yourself or others may occur.

Solution: Keep the gun pointed in a safe direction for 30 seconds. If the round discharges during that time it was a hang-fire. As a precaution, and after the 30 second wait, unload the gun and make sure the offending round is removed and discarded. After that, you may continue shooting.


You pull the trigger. Nothing happens. You keep the gun pointed in a safe direction for 30 seconds to make sure it is not a hang-fire. But the cartridge still does not discharge.

This may be a “misfire”—a cartridge that just does not go off.

Solution. After keeping the gun pointed in a safe direction for thirty seconds to let a hang-fire discharge, remove the round from the gun and discard it. Do not try to shoot it again.

Squib Load

You pull the trigger. Instead of a bang, you hear a pop; it may sound like a cap gun going off. The recoil may be less than normal. Or, the muzzle flash may be less than normal. This may a “squib load”—a partial discharge of the round that does not build as much pressure as a normal discharge.

The danger in a squib load is that the bullet may lodge in the barrel. Pulling the trigger again is very dangerous in this situation. It can blow up your gun and injure you or others.

Solution: If you suspect a squib load condition, keep the gun pointed in a safe direction and stop pulling the trigger immediately. Unload the gun. Run a cleaning rod or dowel through the barrel to make sure it is not obstructed. Remember, there may be a round in the barrel that is not fully discharged; so it is dangerous to put your hand anywhere near the tip of the muzzle. Thus, if you are not trained how to do this safely, ask for help from the Range Safety Officer where you are shooting and follow their instructions. If you are certain you have cleared all obstructions from the barrel, you may continue shooting. If the barrel is obstructed and you know how to remove a squib load without damaging your gun, do so. Otherwise, stop shooting, inform the Range Safety Officer and take it to a gunsmith.

Other Malfunctions

The three malfunctions discussed here are caused by defective ammunition. But you may have a malfunction that has nothing to do with defective ammunition. For example: you may be out of ammunition or the gun may have jammed. These malfunctions may manifest the same way as did a misfire or hang-fire—you pull the trigger and nothing happens. Treat them as an ammunition malfunction. If that does not fix things, we discuss clearing a jammed gun elsewhere.



[1] This picture was created by Avriette and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported License. For more information please see:

[2] This is a close-up of a picture taken by Grombo, licensed under the under the Creative Commons Attribution-Share Alike 3.0 Unported License. For more information please see:

[3] These photos are reproduced with permission courtesy of Max Popenker, Modern Firearms and Ammunition at url:

[4] This photo are reproduced with permission courtesy of Max Popenker, Modern Firearms and Ammunition at url:

[5] Artist Talifero. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unreported license.

[6] This photo is reproduced with permission courtesy of Max Popenker, Modern Firearms and Ammunition at url:

[7] This photo was prepared by ReconTanto and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. For more information, please see: