What Determines the Caliber of an AR-15?

The AR-15 was initially designed to be used specifically with a 5.56x45mm cartridge. However, due to its popularity, there is now a variety of calibers. But what determines the caliber of an AR-15 depends on what you are aiming for with this powerful rifle.

Maybe you are looking for ways to improve hunting, target practice, home defense, or shooting competitions. Whatever your goal is, it is essential to obtain the most suitable caliber for your specific shooting needs.

AR-15 Caliber Choices

The caliber itself is the bullet’s diameter, and when it comes to caliber choices, bigger is not always better, especially when it comes to the AR-15. The following are some of the most popular caliber choices.

1.    5.56 / .223

The 5.56 is the original decade standard for the AR-15 caliber. This round is very light, and considering that the AR-15 holds 30 rounds, the AR-15 can carry a couple hundred 5.56 with no problem at all. 

The best optic for your AR-15!

The .223 is less common but can be used interchangeably with the 5.56; however, the 5.56 does provide a little more power.

The 5.56 / .223 are excellent for using the AR-15 for tactical, home defense, and hunting purposes. This caliber choice is ideal for those living in apartments due to its low barrier penetration.

2.    300 Blackout

The 300 Blackout name is perfect because it is heavier and larger than other calibers. This sturdy caliber is even designed for special operation forces.

Due to the .30 caliber bore, the 300 Blackout offers a broader range of projectile choices and is perfect for hunting. This caliber is exceptional for hunting medium or large game such as deer and smaller bears.

The 300 Blackout can be used with a suppressor and a short barrel for home defense. The short barrel allows for more effortless movement around your home, and the suppressor protects you and your family’s hearing. This caliber is not a good choice if you live in an apartment due to its high barrier penetration.

3.    6.5 Grendel

If you are a recoil-sensitive shooter, the 6.5 Grendel is a great pick. Also, the 6.5 Grendel comes as a .264-caliber and is short enough to fit the AR-15 rifles with ease.

The 6.5 Grendel fires larger diameter, heavier, and more aerodynamic bullets, making it an excellent choice for hunting deer-size game. Due to its marginally larger powder capacity, it cranks out more horsepower than the .223.

The 6.5 Grendel is suitable for precision target shooting and predator hunting.

4.    7.62 x 39

When you compare the 7.62 x 39 to the 5.56, you find that the 7.62 x 39 has bigger bullets, but the 5.56 will be faster. What makes the 7.62 x 39 stand out is its ability to carry more energy into its target as long as the target is within a 300-meter range.

The 7.62 x 39 is an excellent choice for hunting anything up to medium-size game within a 300-yard range.

Another benefit to the 7.62 x 39 is how extraordinarily affordable they are.

5.    .224 Valkyrie

Like the 6.5 Grendel, the .224 Valkyrie also has low recoil, but when you compare the .224 to the .223, the .224 Valkyrie can shoot heavier bullets up to 1,300 yards while the .223 shoots lighter bullets at or below 800 yards.

Like the .223, the .224 is also an excellent choice for hunting. Both can be used for varmint hunting, but the .224 is better for more extended range targets past 800 yards. This advantage is due to the flatter trajectory and higher ballistic coefficient of the .224, making it supersonic at a longer range.

If you are a competitive shooter and routinely shoot out to 1,000 yards, the .224 Valkyrie should be your number one choice.  

Round Out Your AR-15 Necessities

The AR-15 is a powerful piece of machinery and to keep it operating as efficiently as possible requires other necessities.

Another essential element to consider when owning an AR-15 is making sure you have proper tactical gear, which provides highly durable products to hold and safely transport your AR-15 essentials.

A primary necessity for an AR-15 is obtaining the right magazine. The best magazine will feed bullets into the chamber reliably without any malfunction.

It is also vital to maintain and clean your AR-15 because, over time, multiple firings, powder residue, and grime can build up, which ultimately can affect the gun’s performance. This unwanted outcome can lead to unreliable and unpredictable performance when it might be most needed.

Keep your AR-15 clean, accessorized, and stored properly so that you can enjoy and get the most out of this incredible piece of equipment.


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Tactical Gun Review, along with Texas Outdoors Network, is published by Michael Coker and Charles Coker.

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