Caliber Closeup: Guide to .223/5.56 Bullet Weights

The .223 Remington was designed in 1962 and quickly adopted by the U.S. Military as the 5.56mm NATO cartridge. Since that time, it has only gained popularity with shooters around the world using it for a variety of tasks. This versatility has given life to many different .223/5.56 rounds with uniquely performing projectiles.

One thing you may not have noticed is the different bullet grain weights. Whether you’re looking for the best accuracy or simply tailoring your ballistic performance, you should pay attention to bullet grain weight. You should also take note of your rifle’s barrel twist rate, as this directly impacts performance with different weight bullets. 

Federal Ballisticlean 42-grain .223
Federal’s Ballisticlean delivers the same accuracy and reliability as standard FMJ rounds, but with a non-toxic, lead-free frangible projectile

Bullet Weight and Twist Rate

Twist rate is the measure of how long it takes for the barrel’s rifling to make one complete rotation. This spins the bullet for an equal number of rotations given the length of travel. For example, a 1:10 twist rate denotes that the bullet rotates one complete cycle every 10 inches. Therefore, if you have a 20-inch barrel, the projectile will complete two full rotations as it travels down the barrel. 

In general, faster twist rates work better with heavier projectiles, while slower twist rates are optimized for lighter bullets. If your barrel’s twist rate is too slow, the projectile won’t fully stabilize. If the twist rate is too fast, it may overstabilize the round. Both result in a loss of accuracy and an unhappy shooter. 

Since rifles shoot farther distances, twist rate has more of a noticeable effect on your projectile’s performance. Depending on what type of ammunition you will primarily shoot, you’ll want to select a barrel with a compatible twist rate. 

35–45 Grains

Lighter bullets travel faster and tend to have a flatter trajectory (given good weather conditions). The increased velocity makes them great for small game and varmint hunting where you have to be faster than your target. Lightweight bullets also produce less recoil than heavier rounds. 

The lightest weight bullets for the .223 I could find are 35 grains. Hornady offers a Superformance Varmint round with its specialized lead-free NTX bullet. The cartridge is designed to deliver match accuracy with rapid fragmentation, while increasing velocity. This round is screaming fast at around 4,000 fps at the muzzle, which works great for plinking varmints from distance. 

Hornady Superformance Vermint 35-grain .223
Hornady offers a Superformance Varmint round with a specialized lead-free NTX bullet that’s designed to deliver match accuracy with rapid fragmentation.

40-grain rounds are a bit more common. SIG Sauer offers an Elite Performance Varmint round with a tipped hollow point that clocks 3,650 fps. Fort Scott Munitions has a 40-grain TUI projectile that is designed to “Tumble Upon Impact,” increasing the size of the wound channel and creating more tissue damage. Both have devastating terminal effects. 

Federal’s Ballisticlean is available with a 42-grain Reduced Hazard bullet intended for training. Ballisticlean delivers the same accuracy and reliability as standard FMJ rounds, but with a non-toxic, lead-free frangible projectile that reduces airborne contamination and splashback from steel targets. 

Remington’s UMC JHP is available in a 45-grain option that squeezes out a bit more velocity than a typical 55-grain load. It works great for small-game hunting or defense against predators such as coyotes and wolves. 

These ultra-lightweight .223 grain weights are best used with slower 1:14 or 1:16 twist rates. 

50–55 Grains

The majority of .223 Remington bullets start around 50 grains, with the 55-grain being the most prevalent. 55-grain is great for general use and it’s what you’ll find available for most of your cheap range ammo. Virtually every maker has their offering, and most perform generally the same, but I have a slight preference for Armscor or Fiocchi, likely because of habit more than anything else. 

Slightly lighter-weight offerings are available in specialty rounds. The weight difference is likely a result of the projectile design. Federal and Fiocchi offer 50-grain hollow point rounds for hunting and defense. Both are good performers worth a shot. 

Fiocchi Field Dynamics 50-grain .223
Fiocchi Field Dynamics is great for hunting.

Nosler’s Varmageddon features a 53-grain tipped flat base that is designed for the high-volume varmint hunter who demands the utmost in precision and performance. The projectile incorporates a special lead-alloy core, which combines with the copper jacket to violently expand on impact. 

The best twist rates for 55-grain bullets are 1:10 or 1:12. 

60–69 Grains

Continuing along, you’ll find plenty of .223 Remington offerings with bullet weights ranging from 60 to 69 grains. The 62-grain is the most common, as this is the standard weight selected for military 5.56 NATO ammunition. M855 ammo with the SS109 green tip FMJ, from either Winchester or PMC, is a standard stockpile of the prepper for its consistency and affordability. 

SIG Sauer offers an Elite Hunting cartridge with a slightly lighter 60-grain bullet. The solid copper hollow point is stated to provide consistent 1.8x diameter expansion shot after shot. 

Federal developed a 64-grain Power-Shok with a jacketed soft-point projectile intended to provide good performance while hunting, without hurting the wallet. Further, Federal’s 69-grain Gold Medal Match is a hailed competition round with outstanding accuracy. 

PMC M855 SS109 62-grain 5.56
The 62-grain is the standard weight selected for military 5.56 NATO ammunition.

The best twist rates for 62-grain rounds is 1:8, 1:9, or 1:10. 

70–77 Grains

A heavier bullet will have a faster drop, and therefore is not going to go as far. However, the extra weight gives the bullet more stabilization against wind gusts, which are less predictable. Additionally, heavier rounds tend to have improved ballistics against heavier game. If you want effectiveness for defensive situations, larger game, or combat, you should turn to higher-grain cartridges. 

Heavyweight bullet choices for the .223 Remington hover around 70 to 77 grains. Hornady’s Match 75-grain ammunition is highly regarded among competition shooters for its impressive accuracy. This is a good staple to have for long-range shooting. 

Additionally, its “Black” ammunition is specifically optimized for maximum performance in America’s favorite modern sporting rifles. The load uses Hornady’s Interlock HD SBR bullet that’s designed to excel in the 10.5–11.5-inch barrels of popular short-barreled rifles. It provides exceptional performance either suppressed or unsuppressed, with uniform velocity and trajectory. 

Hornady Black 75-grain 5.56
Hornady Black is optimized for AR-15 rifles with short barrels.

Moving on up, PMC and Buffalo Bore have 77-grain loads designed for hunting small to medium game. With around 1,300 ft/lbs of energy at the muzzle, these are incredibly effective rounds with performance you can count on. 

These cartridges are best used with a twist rate of 1:6, 1:7, or 1:8. 

80–90 Grains

Now for the ultra heavyweights. DoubleTap and Barnes offer 80-grain rounds designed for long-range shooting. Both feature a hollow point projectile with a boat tail design and a high ballistic coefficient. 

Hunting Shack Munitions offers a 90-grain .223 that utilizes the Sierra MatchKing hollow point design. The result is a devastating round more capable of taking down larger game. Notably, the HSM Match won’t fit into most magazines due to the increased length of the bullet and cartridge. 

HSM Match 90-grain .223
Notably, the HSM Match won’t fit into most magazines due to the increased length of the bullet and cartridge.

The best barrel twist rate for these heavier rounds is 1:6 or 1:7. 

Final Thoughts

When deciding on which bullet weights to use in your .223/5.56 rifle, it is important to first determine your intended use. Do you need a high-velocity round for varmint hunting? Do you need something subsonic for suppressor use? Fortunately, there’s no shortage of options in bullet weights and designs for the cartridge, but be sure to go with a quality manufacturer and test your ammo in your firearm. 

What are your preferred .223/5.56 bullet weights? Why? Share your thoughts in the Comment section.

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