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The Best Grain for 5.56

The best grain for 5.56x 44 mm NATO is between 55-grain and 62-grain. These projectile weights have a good balance between accuracy and power and are suitable for a wide range of self-defense scenarios. A lighter weight, such as 45, might be more favorable for indoor target shooting with a 5.56 rifle.

Keep reading to see a breakdown of different bullet grains for 5.56 ammo, as well as some details on what makes different bullet weights better or worse, depending on the situation.

Choosing a Bullet Grain for 5.56

Box of Federal 556 XM855 Ammo

5.56x45mm NATO rounds are a popular caliber used in a wide range of rifles, including the popular AR-15, and famously used by the US military for their standard-issue rifles. The ammo is popular due to its decent stopping power, lower recoil, and lower overall weight compared to larger caliber cartridges. 

One of the most important considerations when choosing a 5.56 round is bullet grain. 

Bullet grain is the weight of the projectile component of an ammunition cartridge. One grain is equal to about 1/7000th of a pound (0.06 grams), and the weight of a bullet can have a drastic effect on the ballistics in flight and upon impact. Lighter bullets will fly farther, but heavier bullets are more wind resistant and can deliver more damage to your target.

There is a wide range of bullet grains available for this caliber, giving you many different options when selecting ammunition for your rifle.

Here’s a YouTube video about the Top 5 Home Defense .223/5.56mm Loads: 

In general, lighter bullets are more suited to things like target shooting indoors, where your shot trajectory won’t be affected by wind. Lighter bullets will shoot straighter at farther distances, but they will cause less damage upon impact compared to heavier projectiles.

An excellent way to determine which grain is better for your rifle is to go by the twist rate of the rifling. Tighter twists will be able to stabilize heavier bullets. A 1:14 twist rate, for example, is suitable for bullets between 45-55 grains. 

Rifles with a twist rate of 1:9, by comparison, are suitable for bullets weighing up to 77 grains. Using lighter bullets with tighter twist rates can also over-stabilize bullets, negatively affecting accuracy.

Projectiles on the heavier end of the spectrum (90 grains and up) can potentially be longer than regular 5.56 rounds. In these cases, your rifle will need to be modified to handle the dimensions of the cartridges.

  • 40-Grain: 5.56x 44 mm NATO rounds do come with lighter bullet grains, but 40-grain is a good starting point for small game and home defense. 40-grain bullets are suitable for rifles with a 1:9 twist rate and typically have muzzle velocities up to around 4000 fps.
  • 55-Grain: 55-grain bullets were used in the M193 cartridge by the US Army until the M855 cartridge was standardized in 1982. 55-grain bullets are considered a good middle-ground for home defense and plinking.
  • 62-Grain: 62-grain bullets are used by the US Army in their M855 green-tip cartridges. The increased weight gives the bullet more penetration and makes it more accurate at shorter distances or in windy conditions. 
  • 77-Grain: Suitable for rifles with a 1:7 twist rate, 80-grain bullets pack more of a punch than lighter grains, but at the expense of range and recoil. This is considered the maximum bullet weight recommended for an AR-15 since the 1:7 twist rate might not stabilize bullets weighing more than 77 grains.
  • 112-Grain: This is the heaviest bullet available for 5.56×44 NATO rounds. Used in the Atomic Tactical Cycling Subsonic round, the bullet is meant to tumble as it flies for increased damage upon impact. These bullets have slower muzzle velocities and are unsuitable for shooting at longer ranges. 

These bullets are longer than a regular 5.56 bullet, and so most rifles chambered in 5.56 need to be customized to fit this larger ammo.

Final Thoughts

5.56×44 mm NATO is a widely available round with a good balance between stopping power and accuracy. The rounds are popularly used in AR-15 rifles, which perform well with bullets weighing between 45 and 77 grains, depending on the twist rate of the rifling.

55-grain is considered a good middle ground for self-defense or home defense. If you’re shooting competitively indoors, you may want to go with a lighter bullet for increased accuracy and range.

If you have any questions or concerns, feel free to fire away in the comments section.

For more, check out Bullet Grain Chart By Caliber.