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AR15 Ammo 101: Everything You Need to Know

AR15 Ammo 101: Everything You Need to Know
May 4, 2023 849 view(s)

AR15 Ammo 101: Everything You Need to Know

AR15 is the most popular firearm in the United States due to its customization possibilities.

In most cases, AR15 uses 5.56x45mm NATO or .223 Remington cartridges.

However, when you take a closer look at available ammo for your AR15 rifle, you can see there are more types available than those two mentioned above.

On the other hand, to shoot specific rounds you’ll need barrels made for those rounds with some exceptions where you can use one barrel for multiple calibers.

Table of contents:

  • AR15 Ammo Calibers
  • Bullet Grain in Short
  • Choosing the Right AR15 Ammo
  • Best AR15 Ammo
  • Tips for Getting the Most Out of Your AR-15 Ammo
  • Final Words

AR15 Ammo Calibers

Let’s see what calibers AR15 rifles can use:

  • .223 Remington
  • 5.56x45mm NATO
  • .300 AAC Blackout
  • 6.5 Grendel

Although .223 and 5.56 NATO are physically similar, there are still some differences between them.

Now we will see the differences between these calibers and show more details to make it easier for you to understand and choose the right ammo next time.

.223 Remington chamber

This is the most commonly used AR-15 ammo.

.223 Rem ammo rounds are lightweight and have high velocity making them a great choice for target shooting, varmint hunting, and self-defense.

The .223 Rem bullet usually weighs between 40 and 77 grains and can travel at speeds of up to 3900 feet per second.

However, these rounds are not recommended for hunting big animals as it lacks the necessary energy to take them down.

5.56x45mm NATO

Very similar to the .223 Remington, the 5.56 NATO round is at first a military cartridge.

It has similar characteristics like high velocity and it’s lightweight too.

However, the 5.56 NATO round produces more pressure compared to the .223 ammo round.

The weight of this bullet is also 40 to 77 grains with a maximum speed of up to 2900 feet per second.

Now, lots of people ask if they can shoot .223 Remington and 5.56 NATO interchangeably. Let's check chambers for those rounds:

  • .223 Chamber: can fire .223 Remington only.
  • 5.56 Chamber: can fire both.
  • .223 Wylde Chamber: can fire both.

.300 AAC Blackout

The 300 Blackout round is a relatively new bullet out there and it’s made to be used in AR15 rifles.

Compared to 5.56 and 223 Remington, it has a heavier bullet with a weight between 110 and 220 grains, while it’s slower and travels up to 2300 feet per second.

These rounds are great for hunting and tactical applications, especially for hunting larger animals.

Also, this round can penetrate barriers too.

6.5 Grendel

This one is a relatively new cartridge made for long-range shooting.

Round is heavier than .223 and 5.56mm and it’s made for tactical applications and hunting.

The bullet weighs between 90 and 130 grains while the travel speed is 2700 feet per second. For comparison, 300 Blackout travels at 2300 feet per second, while 223 and 5.56 at 3900 feet per second.

6.5 Grendel rounds are great for hunting larger animals because of their heavier weight and slower velocity.

Read more:

Bullet Grain in Short

Bullet grain refers to the weight of a bullet, in this case to the weight of the projectile - a part of the cartridge that’s fired from the gun.

One grain is equal to 0.0648 grams.

So, for example, the 77-grain bullet is 4.989 grams.

Choosing the Right AR-15 Ammo

Now, as we passed different types of AR15 ammo, let’s explore what factors to consider before buying ammo.


For what purposes do you plan to use your rifle?

Target shooting calibers like .223 and 5.56 NATO will do the job if you're going for target shooting calibers. You can use these calibers for home defense too.

However, if you’re a hunter going for a big game, you’ll need something stronger and heavier like 300 Blackout or 6.5 Grendel.

Barrel Twist Rate

As barrels come in different lengths and twist rates, you should know that not all bullets perform well with the same barrel twist rate.

The general rule is that lighter rounds perform better with faster twist rates while heavier perform better with slower twist rates.

For example, the 1:7 twist rate is faster than the 1:9 twist rate.

As a reminder, twist rate refers to the number of inches required for the barrel rifling to make one full rotation.

Bullet weight and velocity

Bullet weight affects the projectile trajectory and levels of energy.

Heavier bullets typically have more energy and will effectively take down larger games.

On the other hand, lighter bullets may be more accurate and have a flatter trajectory.

The velocity of the bullet also affects its trajectory and energy. A faster bullet typically has a flatter trajectory and more energy, but it may also cause more recoil.


Recoil can affect your accuracy and can be more or less comfortable to shoot depending on your preferences of course.

Heavier bullets have faster velocities which will produce more recoil as a result.


Some rounds are more expensive than others, so consider your budget when going to buy ammo for your rifle.

If you’re shooting often, the costs of ammo can increase very fast, so act according to your needs and preferences.


Some ammo types may be more difficult to find than others so take this one into consideration too.

Also, always if certain ammo is high on demand or in shortage.

Best AR15 Ammo

List of best AR15 ammo we made:

Rainier Munitions Remanufactured .223 Rem 55gr V-MAX Ammunition

Rainier Munitions Remanufactured .223 Rem 55gr V-MAX Ammunition

One of the standout features of this ammo is its competition grade meaning it’s designed to perform at the highest level possible.

It’s a great choice for competitive shooters demanding the best from their ammo.

The Vmax 55gr projectile used in the ammo is also noteworthy. It’s a high-quality projectile that is known for its accuracy and reliability.

It is capable of achieving high velocities, making it an excellent choice if you’re looking for a fast and accurate projectile.

Another great feature is the clean-burning powder used in its production meaning it produces less fouling in your firearm.

This translates into less cleaning time and a more enjoyable shooting experience.

The ammo is also made with indoor range brass known for being more restrictive than outdoor ranges when it comes to the types of ammo that can be used.

Price: $33.95 (50 rounds)
Buy here!

PMC Ammunition X-TAC 5.56MM 62gr LAP Ammunition

PMC Ammunition X-TAC 5.56MM 62gr LAP Ammunition

The PMC X-TAC features a green tip 62 Grain steel core penetrating bullet that’s sure to deliver impressive performance.

Crafted with a non-corrosive boxer primer and brand new, never-fired brass casing, the X-Tac PMC ammo is carefully quality-controlled in-house by PMC to ensure that you receive a superior product with consistently reliable parts.

For high-volume shooters who love to reload their 5.56mm NATO ammunition, this ammo can be reloaded up to 5 times, making it a budget-friendly option.

With an impressive muzzle velocity of 3100 feet per second and muzzle energy of 1323 ft-lbs, the X-Tac Green Tip ammo is a perfect choice for target shooting and practice, as well as personal protection.

Price: $239.99 (500 rounds)
Buy here!

Rainier Munitions Remanufactured .223 Rem 55gr FMJ Ammunition

Rainier Munitions Remanufactured .223 Rem 55gr FMJ Ammunition

Crafted from a high percentage of once-fired mixed military/commercial brass, this ammo is designed to deliver exceptional performance and reliability every time you pull the trigger.

And with a Hornady 55gr Full Metal Jacket Boat Tail (FMJ BT) projectile, you can be sure that your shots will be accurate and powerful, with impressive muzzle velocity and energy.

What sets this ammo apart is its clean-burning powder and indoor range brass, which makes it the perfect choice for competitive shooting events.

Price: $22.49 (50 rounds)
Buy here!

Tips for Getting the Most Out of Your AR-15 Ammo

Now, after you’ve purchased AR15 ammo, here are some tips to get the most out of both your rifle and ammo.


The more you practice with your rifle, the more comfortable you'll become with it. This will help you become more accurate and more efficient with your ammo.

Clean Your Rifle

It's important to keep your rifle clean and well-maintained. This will help ensure that it functions properly and that your ammo performs at its best.

Use Quality Ammunition

Using quality ammunition can make a big difference in the performance of your rifle.

Cheaper, lower-quality ammunition may not be as consistent or reliable, which can affect your accuracy and overall shooting experience.


The weather can have a notable impact on the performance of your ammunition.

Hot temperatures can cause rounds to expand more, while cold temperatures can cause rounds to contract.

Humidity can also affect the performance of ammunition.

Adjust Your Sights

Different ammo may require adjustments to your rifle's sights. 

Be sure to test different ammunition and make any necessary adjustments to your sights to help ensure that you're hitting your target accurately.

Use a Proper Shooting Stance

Using a proper shooting stance can help improve your accuracy and stability when shooting.

Be sure to use a stance that works well for you and practice it regularly.

Keep Your Focus on the Front Sight

When shooting, it's important to keep your focus on the front sight of your rifle. 

This will help ensure that you're aiming accurately and that you're able to make any necessary adjustments to your aim.

Final Words

If you came this far, you probably know how to choose the right ammo for your AR15 rifle, as well as what to consider when purchasing ammo next time.

The most common calibers are .223 Remington and 5x56 NATO and you’ll find them the most.

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