|
|
|
|
.223 Remington
|
| |
|
| |
The .223 Remington is a sporting cartridge with almost the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a diameter, jacketed bullet, with weights ranging from 40 up to , though the most common loading by far is .
While the external case dimensions are very similar, the .223 Remington and 5.56x45mm differ in both maximum pressure and chamber shape. The maximum and mean pressures for some varieties of the 5.56 mm (different cartridge designations have different standards) exceed the SAAMI maximums for the .223 Remington, and the methods for measuring pressures differ between NATO and SAAMI.
Discussion
Ask a question about '.223 Remington' Start a new discussion about '.223 Remington' Answer questions from other users |
Encyclopedia
The .223 Remington is a sporting cartridge with almost the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a diameter, jacketed bullet, with weights ranging from 40 up to , though the most common loading by far is .
While the external case dimensions are very similar, the .223 Remington and 5.56x45mm differ in both maximum pressure and chamber shape. The maximum and mean pressures for some varieties of the 5.56 mm (different cartridge designations have different standards) exceed the SAAMI maximums for the .223 Remington, and the methods for measuring pressures differ between NATO and SAAMI. The 5.56 mm chamber specification has also changed over time since its adoption, as the current military loading (NATO SS-109 or US M855) uses longer, heavier bullets than the original loading did. This has resulted in a lengthening of the throat in the 5.56 mm chamber. Thus, while .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, firing 5.56 mm ammunition in a .223 Remington chamber may produce pressures in excess of even the 5.56 mm specifications due to the shorter throat.
History
The .223 Remington was developed as an enlarged and higher velocity version of the .222 Remington, which was introduced in 1950 as a varmint cartridge. The .223 Remington was developed specifically for the Armalite AR-15, a version of which later became the U.S. military's M16 rifle.
Cartridge dimensions
The .223 Remington has 1.87 ml (28.8 grains H2O) cartridge case capacity.
.223 Remington maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).
Americans would define the shoulder angle at alpha/2 = 23 degrees. The common rifling twist rate for this cartridge is 305 mm (1 in 12 in), 6 grooves, Ø lands = 5.56 mm, Ø grooves = 5.59 mm, land width = 1.88 mm and the primer type is small rifle.
According to the official C.I.P. (Commission Internationale Permanente Pour L'Epreuve Des Armes A Feu Portative) guidelines the .223 Remington case can handle up to 430 MPa (62,367 psi) piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers. This is equal to the NATO maximum service pressure guideline for the 5.56x45mm NATO cartridge.
The SAAMI pressure limit for the .223 Remington is set at 379.212 MPa (55,000 psi), piezo pressure.
Uses
The .223 Remington is one of the most common rifle cartridges in use in the United States, being widely used in two types of rifles: (1) varmint rifles, most of which are bolt action and commonly have 1-in-12 rifling twist suitable for bullets between 40 and , and (2) semi-automatic rifles such as the AR-15 and the Ruger Mini-14, which are commonly found to have twist rates of 1-in-7, 1-in-12, or 1-in-9. (Most modern AR-15s use 1-in-9 which is suitable for bullets up to or 1-in-7 which is suitable for slightly heavier bullets, but older AR-15s used 1-in-12 twist rates, making them suitable for use with bullets of 55 grains.) The semi-automatic rifle category is often used by law enforcement, for home defense, and for varmint hunting (especially farm and ranch work, after which Ruger named a version of its Mini-14 the "Ranch Rifle"). Among the many popular modern centerfire rifle cartridges, .223 Remington ammunition is among the least expensive and is often used by avid target shooters, particularly in the "high power rifle" category.
.223 Remington versus 5.56 mm NATO
While the 5.56mm NATO and .223 Remington cartridges and chamberings are very similar, they are not identical.
Military cases are generally made from thicker brass than commercial cases; this reduces the powder capacity (an important consideration for handloaders), and the NATO specification allows a higher chamber pressure. NATO EPVAT test barrels made for 5.56mm NATO measure chamber pressure at the case mouth, as opposed to the location used by the United States civil standards organization SAAMI. The piezoelectric sensors or transducers NATO and SAAMI use to conduct the actual pressure measurements also differ. This difference in measurement method accounts for upwards of 137.9 MPa (20,000 psi) difference in pressure measurements. This means the NATO EPVAT maximum service pressure of 430 MPa (62,366 psi) for 5.56mm NATO, is reduced by SAAMI to 379.21 MPa (55,000 psi) for .223 Remington. In contrast to SAAMI, the other main civil standards organization C.I.P. defines the maximum service and proof test pressures of the .223 Remington cartridge equal to the 5.56mm NATO.
The 5.56mm NATO chambering, known as a NATO or mil-spec chamber, has a longer leade, which is the distance between the mouth of the cartridge and the point at which the rifling engages the bullet. The .223 Remington chambering, known as SAAMI chamber, is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber (Rock River Arms) or the Armalite chamber, which are designed to handle both 5.56mm NATO and .223 Remington equally well. The dimensions and leade of the .223 Remington minimum C.I.P. chamber also differ from the 5.56mm NATO chamber specification.
Using commercial .223 Remington cartridges in a 5.56mm NATO chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223 Remington chambered gun due to the longer leade. Using 5.56mm NATO mil-spec cartridges (such as the M855) in a .223 Remington chambered rifle can lead to excessive wear and stress on the rifle and even be unsafe, and the SAAMI recommends against the practice. Some commercial rifles marked as ".223 Remington" are in fact suited for 5.56mm NATO, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it, and signs of excessive pressure (such as flattening or gas staining of the primers) should be looked for in the initial testing with 5.56mm NATO ammunition.
Related cartridges
P.O. Ackley created an improved version of this cartridge called the .223 Ackley Improved. It has the straight sides and steep shoulder typical of the Ackley design improvements, yielding about 5% extra case volume. This in turn provides longer case life, less stretching, and up to faster velocities.
Wildcat cartridge developers have for a long time necked this cartridge up to create the 6mm/223 or 6x45. At one time this round was very popular for varminting and competition but has been replaced by current popular competition cartridges using short fat cases, such as the 6 mm PPC and the 6mm BR Norma.
See also
External links
- by AccurateShooter.com
- by Troy Tiscareno
- by Daniel Watters
|
| |
|
|
