.223 vs 5.56: What's the Difference & Which to Choose? thumbnail image

.223 vs 5.56: What's the Difference & Which to Choose?

80 Percent Arms   |   Feb 17th 2021

Image above showing the 5.56 with a green tip and the red tipped .223 was provided by The Big Game Hunting Blog.

One of the most common questions of new AR-15 owners: .223 vs 5.56, what's the difference? The answer isn't as drastic as you think, and the truth is that most of the time, it won't even matter. However, there absolutely are some key differnces in 223 vs 556, so let's take a look at a more detailed breakdown of the two rounds.

.223 Remington

The .223 Remington rifle cartridge was first used as a commercial hunting round for mid-western varmints in 1957. Its first chambered rifle came out in 1962, developed by the Fairchild Industries, Remington Arms, and several CONARC (U.S continental Army Command) engineers. Today, it is popular among civilian hunters, though a military version, the M193 with 55gr metal jacket was used in the M16.

There are a variety of .223 Remington cartridges, including:

  • Montana gold 55-grain full jacket
  • Sierra 55-grain spitzer boat tail
  • Winchester 55-grain combined technology
  • Hornady 60-grain VMax
  • Barnes 62-grain tipped triple shock X
  • Bossler 69-grain hollow boat tail
  • Swift 75-grain Scirocco II

.223 Features

The .223 has a .222 Remington parent case that is rimless and bottlenecked with a 5.7mm bullet diameter, 6.4mm neck diameter, 9mm shoulder diameter, 9.6mm base and rim diameter, 1.1mm rim thickness, 45mm case length, 57mm overall length, 1.87-milliliter case capacity, 1:12 rifling twist (Military rifles use 1:7 to 1:10 to stabilize longer bullets.), maximum pressure (SAAMI) of 380 MPa, Maximum pressure (CIP) of 430 MPa and a 52000 CUP.

Ballistic Performance

The ballistic performance is measured by the velocity and energy of the cartridge and is dependent on the mass of the bullet. The various bullets include:

  • 36-grain (2g) JHP: Has a speed of 1140 m/s and energy of 1300J
  • 55-grain (3.5g) Nosler ballistic tip: Has a velocity of 990m/s and energy of 1715J
  • 60-grain (3.9g) Nosler Partition: Has a speed of 960m/s and energy of 1796J
  • 69-grain (4.48g) BTHP: Has a speed of 900m/s and an energy of 1814J
  • 77-grain (5g) BTHP: Has a speed of 840m/s and an energy of 1764J

The .223 Remington is used in a wide range of semi-automatic and manual action rifles, as well as handguns, including:

  • Colt AR15
  • Ruger mini14
  • Remington model 700
  • RemingtonXP100

It is one of the most popular cartridges, so much so that it usually takes precedence over all other similar .22 caliber centerfire varmint rifle cartridges.

5.56x45mm NATO

The 5.56 NATO was developed from the .223 Remington in Belgium during the 1970s. It uses a 62-grain metal jacket bullet boasting of a 7-grain steel core for penetration through lightly armored targets such as a U.S M1 WW11 helmet at 800 meters.

Its superior long-range performance (thanks to its higher sectional density and a superior drag coefficient) compensates for the slightly lower muzzle velocity, reducing its fragmentation compared to the .223 Remington. However, the 5.56 NATO brass cases and the .223 Remington’s external dimensions are nearly identical.

5.56 Features

The 5.56 NATO has a .223 Remington parent case that is rimless, tapered, and bottlenecked. It has a bullet diameter of 5.70 millimeters, a 6.43mm neck diameter, a 9mm shoulder diameter, a 9.58mm base diameter, a 9.60mm rim diameter, 1.14mm rim thickness, 44.70mm case length, 57.40 overall lengths, 1.85 cm3 case capacity, 178mm or 229mm rifling twist, small rifle type, maximum (EPVAT) pressure of 430.00 MPa and a maximum (SCATP 5.56) pressure of 380.00 MPa.

Ballistic performance

The ballistic performance of the 5.56 depends on the mass of the bullet.

  • 3.56g(55-grain) XM193 has a velocity of 993m/s with energy of 1775J
  • 4.0g(62-grain) SS109 has a velocity of 948m/s with energy of 1797J
  • 4.0g(62-grain) M855A1 has a velocity of 961m/s and energy of 1859J
  • 4.1g(63-grain) DM11 has a velocity of 856 m/s and energy of 1769J
  • 4.1g(63-grain) GP90 has a velocity of 851 m/s and energy of 1679J

.223 Remington vs 5.56x45mm NATO

The Remington .223 and 5.56 NATO can be compared based on several factors. The differences may be small but cause a large impact on the performance of the cartridges.

  • Dimensions:

    Their external dimensions are basically identical. The case capacities are similar but vary by as much as 2.6 grains. The shoulder and neck length differ however, with the 5.56mm NATO being thicker for accommodating higher chamber pressures.

  • Rifling:

    This factor is expressed in ratio form and must match the bullet design that is the length, weight, and projectile shape. 1:12 means the bullet rotates 360 degrees after traveling 12 inches. The 5.56 *45mm and the .223 Remington can both be shot by the 5.56 mm NATO.

  • Pressures:

    The original pressure for the .223 in 1964 was 52000psi when it was submitted to SAAMI. The current pressure resulted from the change to the Olin ball powder from the IMR. The 5.56*45mm has a pressure of 62,366 psi. This pressure difference is due to the way the pressure is measured. CIP protocols use a drilled case rather than an intact case with a conformal piston. NATO used another procedure to measure. However, when subjected to the same test, the .223 yields peak average pressures of 5000 psi lower than the 5.56 NATO.

  • Chamber:

    The .223 chamber (SAAMI chamber) has a shorter leade compared to the 5.56mm NATO chamber (mil-spec chamber) which has a longer leade. The leade is the distance between the cartridge mouth and the point the rifling engages the bullet. The casings of the leade and chambers are virtually the same size but are not completely interchangeable because a .223 is designed to handle lower pressures.

  • Velocity:

    The barrel length of the rifle determines the muzzle velocity. A longer barrel length yields a greater muzzle velocity while the opposite is true for shorter barrel lengths. The .223 gains or loses 25.7 feet per second for each inch of barrel length while the 5.56*45mm NATO loses or gains 30.3 feet per second per inch of barrel length.

There's also a low cost of acquiring the .223 compared to the 5.56x45mm. The .223 has very little recoil compared to the 5.56 NATO, so it provides more comfort when firing. However, the 5.56 is easier to control with follow-up shots. The .223 has a low ammunition weight, which makes it easier to carry around. Plus, you can carry more ammunition with it. You can shoot a .223 in a 5.56 marked barrel but cannot shoot a 5.56 in a .223 marked barrel.


You need to first decide what cartridge you need for what purpose depending on the task at hand, distance, type of armor, type of rifle, and size of the object being shot at. If you are going on a heavy hunting trip for a buck, a 5.56 is more preferable due to the higher pressure and ballistic performance. Plus, the light weight allows you to carry more ammunition without weighing yourself down. But if you're planning a light hunting job, such as a rabbit, a .223 would be more suitable since its lesser ballistic performance won't destroy your prey.