Definition: The diameter of the gun barrel or the diameter of the bullet fired from the gun.

You will often hear gun owners using the term "Cal," a short form for calibers of bullets. The Bullet diameter is measured in hundredths of inches or millimeters.

For example, a .45 Cal bullet is 0.45 inches in diameter.

Bullet calibers are one among many other features of a bullet. Bullets with the same caliber size might have other features which do not match, such as the cartridge case length, the amount of powder inside the bullet and the bullet weight or velocity.

Before we identify the different calibers of bullets, let us know how you can identify the caliber of a bullet by just looking at it. No one walks around with Vernier calipers to measure bullet calibers. So, how can one know the caliber of a bullet?

How to Read a Bullet Caliber


You can know bullet calibers using the following steps;

  • You need to check the bullet's casing, which is the lower part of the bullet.

  • Turn the bullet upside down so that the bottom is facing you.

  • At the center of the metal, the jacket is a small circle, the firing pin.

  • Around the firing pin is the headstamp, an engraving with the caliber information.

  • Find the number that starts with a decimal point. This is the bullet caliber.

Remember, the bullet caliber is just one dimension of the bullet size.

What of Gauges?


You must have heard of 16 or 20-gauge bullets before. These are dimensions used when talking of shotguns and the shotgun barrel. The fun thing to remember is that the lower the gauge number, the more powerful the bullet. Therefore, a 10 gauge bullet would be more powerful than a 20 gauge bullet.

Today, we will focus more on calibers of bullets.

Now, let us talk about the calibers of bullets because as that is what brings you. Also, we will talk about the different types of bullets and more just after the different calibers, so stick around.

Calibers of Bullets


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Whether you are using your gun for sporting, self-defense or hunting birds, there are some common calibers that you will come across and some rare ones that you may never get to use in your lifetime. We will talk about all of them.

Here is a quick definition of terminologies we may use in some cases.

  • Velocity- The speed of the given bullet in feet/second (fps- feet per second).

  • Bullet weight- Measured in grains. 7,000=1 pound.

  • Price point-How much does one pound cost.

  • Energy- The power of one round.

  • Centerfire cartridges- Primer at the center of the cartridge. (Firearms strike the primer to ignite the cartridge and fire).

  • Rimfire- Primer at the rim of the cartridge case.

Here are the bullet calibers.

1) .22LR


Velocity: 1080-1600 fps

Weight: 30-40 grains

Price point: 0.05$

Energy: 140-160 joules

Remember, we said that the caliber simply means the size of the diameter of the cartridge. Therefore, the features are not general for the .22LR calibers, as you can have other .22LRs that have fewer grain ratings and less or more energy.

The .22LR is the most common bullet caliber of them all. These calibers are meant for both handgun cartridges and rifle rounds. By numbers, this caliber is the most sold in the market. The compact size of these rifle rounds is a favorite among many as they have a high speed and a low recoil.

The .22LR is perfect for beginners because of its ease of use. However, this is the bullet for you if you are a recreational shooter. This bullet is perfect for target shooting and small game hunting. However, when it comes to self-defense, this caliber can do considerable damage to a human being.

The other reason these calibers are perfect for beginners is their low price point. You will not be wasting money on any wasted rounds, and your gun handling learning curve will be much faster.

2) .300 BLK

300 Blackout

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Velocity: 2200 fps

Weight: 125 grains

Energy: 1360 joules

Price-point: 70 cents

Also known as the Three Hundred Blackout, the caliber is quite a new cartridge on the block. The ARs needed a larger caliber, and the BLK is the gift that gave. The advantage that the cartridge has is a great control that it has. Gun owners love the BLK because of how easily you can load it, making it a perfect choice for a situation that would demand you to defend yourself.

Adding an adjustable gas block to your setup makes the 300BLK perfect for range shooting and gives you manageable recoil. The fact that you can add to cartridge to an AR15 pistol makes the cartridge versatile and practical in different situations.

The effective range of the .300 BLK is just under half a kilometer at 460 meters (around 503 yards). This range is perfect for range target shooting. With a drop of only 4 inches at 100 yards, you will have fun with this one.

All other variable factors considered, the .300 BLK is the cartridge you want in your AR15. It gives you a wide range of metal projectile sizes and weights you can use on your gun. All that can be said is good luck to a target within 300 yards of the rifle cartridge.

3) 9mm

 9MM Bullet

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Velocity: 1180-2010 fps

Weight: 115-147 grains

Price point: 25 cents

Energy: 481-729 Joules

This is a rather famous one. Officially known as the 9mm Luger cartridge or the 9x19mm Parabellum, the caliber is used by most law enforcement agencies in NATO countries. The 9mm has been around the block for a while now. Over 100 years is no mean feat and means that the cartridge is effective at whatever it does. It was designed in 1901, produced in 1902 and has been around.

The caliber is perfect for personal defense because it is a low-power round with low recoil. As a result, staying on target in high adrenaline situations like target shooting competitions will be easier.

The 9mm is great for firearms training because of the fair pricing at only 25 cents. In addition, this caliber is one of the common bullet calibers allowed for concealed carry. Your gun will be able to hold 15 of these rounds.

4) .25 ACP

.25 Caliber

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Velocity: 760-900 fps

Weight: 35-50 grains

Energy: 85-89 joules

Price point: 50 cents

The ACP in the title stands for automatic colt pistol. Compared to the .22LR, the .25ACP is more powerful because of its sheer size and weight. The improvements make the caliber at least twice as powerful as the .22 cal. However, it comes at a cost because of the additional features, making the caliber more expensive.

Handling the 25ACP has its advantages and downsides. The good side of using the .25 ACP is that it can fit into smaller pistols that are chambered for this caliber. This is why John Browning developed the caliber to sort out the problems that the .22 had.

Is the .25ACP good for self-defense? Well, it has a small size and will probably fit in a gun that will fit in a small purse. Probably undercover police officers might find some use for it and feel safer in certain situations.

The downside might be the unpopularity of the guns that take these caliber rounds. They were popular handgun cartridges in the 80s, but better and more reliable firearms are available today. Availability is a huge factor when looking at cartridges. You want to own ammunition you can enjoy using and can count on.

This can be one option you can have up your sleeve.

5) .30 Carbine

30 Carbine

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Velocity: 2000fps

Weight: 110 grains

Price point: 40 cents

Energy: 1300 joules

Though not in great use today, this caliber was the main choice during world war ii. If you are using an M1, you will love using these rounds. The efficiency of using these calibers has stayed high, and being the first self-defense option in the market, their ease of use will keep them around for some time.

The calibers are easy to load and are lightweight. Other calibers are available today, but the reliability can hardly be compared. You can use fast-burning gun powder because of the caliber's accuracy.

The Carbine was designed to be lightweight and efficient. For this reason, it was preferred for use by soldiers who did not need extra weight because they had other errands to run. As a result, the Carbine is one of the most used bullet types, but just like the .25ACP, it is a bit outdated.

6) .380ACP

380 ACP

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Velocity: 1025-1280 fps

Energy: 280-419 joules

Price point: 45 cents

Weight: 45-100 grains

This is a popular choice for self-defense due to its reliability. In addition, the rounds are easier to handle and are a cheaper option than other cartridges on the market. The .380ACP is used mostly as a backup weapon by the United States military and police forces because it is not as powerful as the 9mm. For this reason, the cartridge makes for a great self-defense weapon that can be concealed and still carry a lot of rounds at once.

While the power is low, the recoil is also low, and the penetration is deep, making the cartridge a better option for control. In addition, the cartridge will not be a hassle to carry around, and you will probably only notice you have it when you need it. This is your best conceal carry choice.

The .380, 38 special and the 9mm are rather similar. The main difference would be the gun powder each has or uses.

7) .40 S W

40 S&W

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Velocity: 1050-1130 fps

Weight: 155-180 grains

Price Point: 30 cents

Energy: 628-797 joules

What would you trade when it comes to choosing a cartridge? Would you take more power, less recoil and weight over accuracy and quickness or vice versa? This option that the .40 s w gives you over the 9mm. For this reason, the FBI and the police tend to switch one of the two for the other, with some officers preferring the .40 s w and others the 9mm.

With a lightweight design, the cartridge has gained more popularity within the law enforcement community and with civilians. However, most people will choose speed and accuracy, which is why the .40 s w will come second after the 9mm most of the time.

8) .45 ACP

45 ACP

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Energy: 483-1124 joules.

Price point: 40 cents

Velocity: 835-2038 fps

Weight: 90-230 grains

The .45 ACP is not only known for its size and great stopping power; it has a service history that goes way back in the day. This is the cartridge that was designed for the 1911 pistol. The price point is favorable, making it a great choice for a beginner. The downside of learning this caliber is that you might have trouble controlling it at first. It will take quite some time to build skills with this cartridge compared to the other options.

Long-distance shooters might not find this caliber a favorite option. However, it is a common caliber and a fair place to start.

9) The .3o8

The .308

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Velocity: 2600-2700 fps

Energy: 3300-3500 joules

Price Point: 75 cents

Weight: 147-175 grains

You will understand just how powerful these rounds are if you have read the specs above. The .308 is the preferred caliber of choice by snipers all over the world because of the sheer range that it has over other cartridges. The cartridge is also known as the .62x51mm, in case you are unfamiliar with this caliber.

The military version of this cartridge is 7.62. According to some people, the .308 is slightly larger in shape and better looking than the NATO round.

If you have the target locked in place, the more than average recoil is not a problem compared to what you can achieve with the cartridge. However, if you are looking for power, this is your pick. The price point is worth every shot.

10) .223

.223 Remington

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Velocity: 3100 fps

Energy: 1770 joules

Weight: 55-62 grains

Price Point: 30 cents

This caliber (also known as the .56×45 mm) is slightly controversial because it is considered controversial. Hunting is not advised unless you shoot small garden animals like rats. This is because the caliber punches a soft shot.

This round's advantage is the long-range capabilities, making it perfect for self-defense. Apart from being a home defense round, the cartridge has moderate recoil and great accuracy.

Be sure you know your state laws because some states do not allow this cartridge for hunting.

Parts of a Cartridge

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It is important to know the cartridge more than just the caliber. The same cartridge can have different velocities, energy ratings and bullet weight classes. Therefore, it is vital to know the parts of a cartridge before you go for a particular one hoping it will fit in your firearm.

The cartridge is not the same thing as the bullet. The bullet is just a component of the ammo. The cartridge has four basic parts.

a) The Case

The case holds everything together, including the primer, the bullet and the powder. All these things work together to propel the projectile, which is the bullet. In addition, the case is sized to fit precisely inside the gun barrel. Modern firearms have different barrels, and the cases are made to fit appropriately in different situations.

b) The Powder

The gun powder has come a long way. From the days when you had to pour them inside the barrel and poke them with a stick to the more recent firearms that come already stuffed in the cartridges. The powder can now be stored safely in the cartridges without worrying about the powder getting corrupted.

The gun powder, once ignited, burns rapidly and provides the fuel that propels the bullet. When the powder burns, the gas in the barrel expands and forces the bullet to leave the gun through the muzzle.

The gun powder is also known as the black powder and is made up of carbon, sulfur and potassium, which are reactive when ignited.

c) Primer

The primer initiates the combustion that occurs on the powder. The primer can be electrically ignited or hit by force from the firing pin. The primer is encased in the shell and is a quick-burning charge that triggers the powder's reaction.

d) The Bullet

The bullet is the most important part of the cartridge as it gives the gun its main purpose. The bullet is the projectile that is sent off to execute a hit on a target. One cartridge caliber can take more than one bullet size. The bullet weights can differ depending on the grains you are going for. These factors can differ while the cartridge remains the same as long as the caliber can take the bullet.

There are two types of bullets:

i) Open Tip Bullets

These are sometimes confused for hollow-point bullets, which they are not. Please take note of this.

Open Tip Match

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The OTM (open tip matches as they are sometimes called) have an opening at the top due to how they were manufactured. Long-range shooters love these because of their stability. However, if your target is far, this is your best rifle caliber choice for you.

ii) Full Metal Jacket

These bullets, also known as the FMJ, are the most popular choice in the market today. The bullet's center has a soft metal core but is covered by a harder metal on the outside.

Full metal jacket bullet

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It is good to know when and how to use such a round. If you are not a fan of lead deposits in your barrel, these are the bullets for you. However, their downside is that they are not the best for self-defense.

iii) Soft Point Bullets

Soft-Point Bullets

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These bullets expand once they hit the target. The unique feature is that the bullet has a soft core surrounded by a hard metal, but not at the tip. You have to be careful around these bullets because they likely cause large wounds. The soft point is not a large bullet, but you can be sure the hit on the target will be larger than the bullet diameter.

The open tip is the main difference between this bullet and the FMJ.

iv) Ballistic Tip

Polymer Tipped Ammo

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The ballistic tip has a lot of material physics solutions that the other bullets do not have. The design is a line of hollow points. However, at the hollow point, plastic is placed at the tip. This plastic improves the terminal expansion of the bullet when impacting the target. As a result, the tip pushes inwards and forces the bullet to expand while preventing debris collection at the tip.

The bullet weights more at the back, increasing the stability and agility.

v) Hollow Point

Hollow points are hollow for a reason. The hollow point collects more debris as it expands and passes through a target, causing more damage if you are at close range and do not require the advantages of a ballistic tip; all the best of luck to the target.


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You can find jacketed hollow points in the market. The difference with the hollow point is the rather shallow hole at the top. The jacket extends to the top in these kinds of bullets.

You further have a semi-jacketed hollow point. The jacket in these hollow points does not extend to the top. Functionally, the jacketed and the semi-jacketed are different. The semi-jacketed expands to form a really large mushroom and will cause much damage. On the other hand, the JHP penetrates deeper into the target.

The SJHP is used mostly in revolvers chambered ammunition such as the .357 magnum or the 38 special.

vi) Wad Cutter


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These are unjacketed options and are normally used for target practice. The semi-wad cutter expanded like the semi-jacketed bullet and was used by the police before the jacketed bullets were brought into the market.

vii) Boat Tail

boat tail

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This type of bullet is one of the preferred rifle calibers because of its efficiency and agility. The design looks like a combination of a bow and a stern of a boat and works best in competitions or hunting.

viii) Bonded Bullet

Bonded bullet

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This type of bullet is chemically bonded to a lead alloy core and will penetrate a target deeper than the other bullets. The bullet will not disintegrate like its counterparts but will remain intact as it penetrates the target. If you are hunting dangerous game, this should be your go-to option.

ix) Steel Core

steel core ammo

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This is your armor-piercing bullet. The steel core can sometimes e confused with the ballistic bullet, hence why it is dipped in green paint at the tip. The bullets are sometimes referred to as the green tip.

These bullets are not allowed at the gun ranges because of the damage they can do.

Note: A bullet that has a flat tip can be referred to as a flat nose or a truncated cone bullet.

Final Thoughts

These calibers might sound intimidating to understand at first, but once you wrap your head around them, you will find it a beautiful craft with your perfect combination for bullets. A bullet needs a combination of cartridge parts that suits a given situation, and you can start crafting your perfect bullet.

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