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The Best Grain for AR-15

The Armalite Rifle is a great all-around firearm chambered most commonly in 5.56x45mm (0.21×1.7 in) NATO or .223. Choosing the right projectile weight is essential because the weight of the bullet will affect your accuracy and power at different ranges.

The best bullet grain for an AR-15 is around 55 grains. This is a good middle ground between the accuracy of lighter bullets and the power of heavier bullets. Heavier bullets may be preferable when hunting larger game.

The most important considerations when choosing a bullet grain for your AR-15 are range, twist rate, and what you’re actually shooting at. Keep reading for more information on the best bullet grains for different AR-15 rounds, and other things you need to know about bullet grain and rifle twist rate.

What Is the Best Bullet Grain for AR-15?

An AR 15 Pistol With Rounds

The most common calibers for an AR-15 are .223 and 5.56x44mm (0.21×1.7 in) NATO. Both are fairly comparable in terms of how bullet grain affects their trajectory. The more important factors when selecting a projectile weight are the twist rate and what you’re actually shooting at.

Lighter bullets are more accurate at longer ranges but have less power and are more susceptible to being blown off course by the wind. Heavier bullets are less accurate at long ranges but pack more of a punch and aren’t affected as much by wind. The twist rate of your rifle will also determine the bullet weights that it’s effective at stabilizing.

Conversely, target shooting indoors would benefit more from a lighter bullet. This is because when indoors, you don’t have to worry as much about the wind messing with the trajectory of your shots. Lighter bullets are also more accurate at longer ranges.

.223 Versus 5.56

I’ve established that 5.56 and .223 are the best bullet grains for AR-15. They seem to be similar cartridges at first glance, but they do have their differences. 

  • 5.56 rounds typically have thicker walls, leading to an increased pressure due to the powder combusting in a smaller space. Rifles chambered in 5.56 are specifically designed to deal with this increased pressure, while rifles chambered in .223 may not be.
  • One other difference is that .223 Remington rounds are standardized by the Sporting Arms and Ammunition Manufacturers Institute, whereas 5.56 rounds are not. This won’t have much of an effect on the optimal bullet grain for your rifle, but it’s an important consideration when making an ammo selection nonetheless.
Full Magazine of 556 Ammo Laying on a US Army Uniform With Dog Tags

Twist Rate

The twist rate refers to the rotations of the rifling on the inside of a barrel. It’s usually expressed as a ratio. For example, a 1:9 twist rate means the rifling makes one full rotation every 9 inches (22 cm). The most common twist rates for an AR-15 are 1:7 or 1:9, but other twist rates such as 1:12 also exist.

The tighter the twist rate, the more the rifling will stabilize your projectile. However, if your twist rate is too high relative to the weight of your bullet, it can actually over stabilize the bullet, leading to a decrease in accuracy.

1:7 twist rifles are suitable for stabilizing bullets between 50 and 90 grains. This is actually the twist rate used by the US military in their AR variants, along with 62-grain projectiles.

Hunting Versus Defense

When using an AR-15 for hunting, it’s recommended that you go with a heavier bullet compared to target shooting. This is because a heavier bullet will pack more of a punch, and it’ll be more accurate at medium distances under windy conditions. Lighter bullets are suitable for small game but aren’t as effective against medium-sized game such as deer.

If you’re going for self-defense, I suggest you use something between 55-62 grains. This is a perfect middle ground between stopping power and accuracy. In fact, the US military uses 62-grain projectiles in their standard-issue rifles.

Final Thoughts

Whether you’re using your AR-15 for hunting, self-defense, or just plinking away at the range, choosing the right bullet grain can make a noticeable difference in accuracy and effectiveness. AR-15s are usually chambered in either 5.56 or .223, and both generally have a similar range of effective projectile weights.

For hunting with an AR-15, 55-60gr is considered a good middle ground between accuracy and stopping power. For other uses, it’s important to consider the twist rate on your rifle. A 1:9 twist rate can effectively stabilize bullets up to around 77gr.

For more, check out Bullet Grain Chart By Caliber.