This article comes from Fenix Ammunition and is reprinted with permission gained via Twitter DM on 2/17/21. Fenix Ammunition has recently made the news because it forces anyone wishing to do business with them to check a box certifying that they did NOT vote for Joe Biden. It is largely symbolic but I also think it does make the person who did vote for them think harder about their choice. They have a great Twitter and they are outspoken Patriots. Check out their products here and, if you order anything, let them know we sent you!

By the end of the Second World War, the effectiveness of the German MP43 assault rifle (see 7.62×39) had become well known. The major breakthrough in the MP43 design was the use of a scaled down version of the full powered 7.92 (8×57) German infantry cartridge. The resulting 7.92×33 Kurz cartridge enabled a trained soldier to maintain reasonable control of the MP43 rifle set to fully automatic fire. Ammunition for the MP43 was light to carry and the soldier could therefore carry more into combat. These factors combined made the MP43 an effective assault weapon.

MP-43, which is nearly identical to the STG-44

Following the war, the major military powers of the world began experimenting with scaled down cartridges and prototype assault rifles. With the formation of the NATO pact alliance, members agreed to work towards a universal rifle and cartridge design for all allied infantry. After several design proposals allied powers found themselves divided into two camps. The countries of the commonwealth were very much in favor of a 7mm cartridge which would have duplicated today’s 7mm08 while the U.S, the super power of the allied world, insisted on a .30 caliber cartridge, preferably a scaled down version of the .30-06.
Ultimately, the U.S ordnance department convinced all NATO pact members to adopt the T44 cartridge, now known as the 7.62 NATO or in its commercial guise, the .308 Winchester. Yet for all of the pushing for a .30 caliber cartridge, a sub committee of the U.S Ordnance department (project SALVO), continued to experiment with small caliber cartridges, leaning towards the .224 caliber.
After promising reports from project SALVO during the mid 1950’s, the US Ordnance Department invited cartridge designers to develop a military round based on the .224 caliber with a prerequisite that the projectile must stay above the speed of sound at 500 yards. In 1957, Robert Hutton, technical editor of  Guns and Ammo magazine designed a potentially suitable cartridge. Hutton’s cartridge was based on a lengthened version of the .222 Remington, loaded with a 55 grain prototype bullet made for Hutton by Sierra Bullets.

By the later 1950’s, firearms designer Eugene Stoner had achieved partial success with his AR 10 rifle.  The  Armalite AR 10 was radically different from other rifles of the day using a combination of alloys and polymers to create a light and compact assault rifle. Unfortunately for Stoner, the lightweight AR 10 chambered in 7.62 NATO produced too much recoil for controlled automatic fire however, the excellent rifle design was noted by various parties. After receiving the invitation to design a .224 caliber rifle, Stoner re-chambered the AR 10 to Hutton’s .224 caliber cartridge and submitted the combination for testing during 1958. The combination was well received however the final decision would have to come from the upper echelons of the U.S government. By this time Armalite had lost a great deal of money through investing in Stoners AR 10 and AR 15 and decided to sell the rights to his designs. Colt firearms purchased these rights and continued to pursue marketing the AR 15.
In 1963, the communist conflict in Vietnam grew with rapid momentum. The U.S had so far committed a small force to Vietnam to inhibit the socialist movement however the Ordnance department did not have enough manufacturing resources to arm the full force that would soon be required. To this end U.S secretary of defense Robert McNamara made several major decisions that would dramatically alter U.S Ordnance permanently. The Springfield Armory and production of the M14 rifle was dissolved and rifle production turned over to the private sector. Colt was given the contract to supply the AR 15 rifle to U.S forces without further ado.
The AR 15 rifle and cartridge were formally adopted in 1964, designated the XM16E1 (common name M16) rifle and 5.56 Ball M193 cartridge. Velocity for the 55 grain bullet from the 20” barrel of the M16 was rated at a true 3200fps. The rifle was used in small numbers up until 1965 when both the war and production of the M16 rose dramatically.

From the very outset of its adoption the M16 was plagued with troubles. Stoner had designed the original AR 15 with a very slow barrel twist rate of 1:14 which was literally a doubled edged sword. By using a slow twist barrel the 55 grain bullet was only just stable in flight, producing a small degree of yaw. On impact the bullet would immediately tumble and render a wide, incapacitating wound. This was initially considered a brilliant design premise but some rifles produced too much yaw and were very inaccurate at longer ranges. McNamara ordered that the twist rate be changed to 1:12 before final adoption of the rifle in 1964. This cured longer range accuracy problems but completely destroyed the stopping power of the 55 grain bullet which now poked needle holes through its victims. Nobody questioned the potential consequences of this move and ignorant of the facts, Ordnance brass continued to believe and promote the M193 as a highly effective cartridge.
Major troubles next appeared in 1965 when the M16 rifle was adopted en masse by the thousands of U.S soldiers entering Vietnam. Up to 50% of the rifles were jamming in the field and hundreds of U.S troops were killed while desperately trying to clear jammed chambers. Troops were further demoralized when neither the military brass or Colt would look into the problem seriously. Instead, troops were accused of not cleaning their rifles properly which had lead to powder fouling. The powder fouling was cited as the reason why cases were not being extracted from the rifle’s chamber.
After continued complaints, both the Ordnance department and Colt representatives eventually began to look at the problem although still with a measure of apathy. The M16 then underwent some design alterations however, the cause of the jamming problem had still not been identified. A new model M16A1 now featured a chrome lined chamber and bore in an effort to produce smoother feeding. Other alterations were made to the M16, but without any true knowledge of the underlying problem, these added unnecessary weight to the rifle which was now only a shade lighter than the M14.
It was several years before the underlying cause of the M16’s jamming problem was properly identified.  Ordnance staff discovered that Stoner and ammunition manufacturers had initially tested the AR 15 using extruded (stick) powder but when the Vietnam conflict exploded, ammunition manufacturers adopted the more readily available ball powder. The ball powder produced a longer peak chamber pressure with dire effects. Normally upon firing, the cartridge should expand to seal the chamber (obturation), then contract and then be extracted. With ball powder, the case was still obturated due to the longer peak pressure. The ejector would then fail to extract the case, tearing through the case rim, leaving the obturated case behind.

In 1970, the U.S government announced its standardization of the M16A1 rifle and cartridge to NATO allies. The news was received with a degree of resentment, especially for those countries who had committed precious resources to the T44 cartridge and rifles. Nevertheless, as finances allowed, all NATO pact members eventually adopted the 5.56mm cartridge. Most countries adopted the M16A1 rifle while a few worked with their own rifle designs.
During the 1980’s, the 5.56mm cartridge was officially standardized as a NATO cartridge. A remaining weakness of the M193 load was its extremely poor penetration through heavy clothing at ranges of 500 yards and beyond. The Belgium military provided a solution with their 62 grain bullet design. The Belgium load became the standard NATO ball, designated the 5.56 NATO. Muzzle velocity is 3025fps from a 20” barrel. The M16 rifle then underwent a further upgrade to a 1:7 barrel twist rate to utilize the new load. The new model rifle was designated the M16A2.
Today, the M16 rifle design remains in service world wide. The current model is designated the M16A4 and features a Picatinny scope rail with most M16 rifles now wearing a scope. Several countries have however moved away from the M16 rifle, some towards more radical designs, notably Great Britain who utilize the SA80 along with Australia and New Zealand who currently use the Steyr AUG rifle.
The 62 grain load is still used by all NATO members however its shortcomings are a continual source of frustration to soldiers engaged in combat. Nevertheless, current allied military strategy does not require a great deal from infantry weapons. The standard operating procedure (SOP) used in the war against terrorism is somewhat simple and predictable. Allies are required to locate terrorists, surround the target and provide suppressive fire while awaiting either an air strike or artillery support. The 5.56 NATO is adequate for this role and also excels during house to house combat, at point blank ranges.
In 2002 the US military and Remington began experimenting with cartridges to deliver more effective power for special operations command (SOCOM) soldiers. Eventually the .270 caliber (.277″ or 6.8 mm) was settled on, using a case based on the 30 Remington. In 2004 the new cartridge was announced as the 6.8 Remington. The 6.8 fires a 115 grain bullet at 2800fps, in 24″ test barrels, and has a similar trajectory to the 7.62 (.308) with a substantial increase in energy at all ranges over the 5.56. The 115 grain bullet of the 6.8 has a ballistic coefficient of about .340 and is loaded to 55,000psi. This cartridge is still in an experimental stage of use (2009). Velocity from a 20” military barrel is probably much closer to 2650fps.

As a sporting cartridge, the 5.56 cartridge was adopted by Remington in 1964, the same Year McNamara officially adopted the cartridge for the U.S military. The sporting version was named the .223 Remington and promoted as a varmint cartridge, ironically, because almost every U.S state does not allow the use of .22 centerfires of medium game due to insufficient killing power. Nevertheless, the NATO standardization of this cartridge has ensured its long term popularity with hunters and the .223 Remington is now a major selling cartridge.
Like the .222, when using 40 to 55 grain projectiles, the .223 produces a broad but shallow wound channel at ranges less than 100 yards. Beyond 100 yards, especially between 200 and 250 yards wound channels tend to be much narrower than cartridges of 6mm upwards. A major difference between the .222 and .223 is that both Federal and Winchester produce loads for use on medium game. Nevertheless, if using the .223 on medium game, it is very important to try and avoid major shoulder bones to aid bullet penetration and ensure that wounding occurs exclusively within vitals.

.222 vs .223

As a varmint or target shooting cartridge, the .223 is an outstanding performer, inexpensive and capable of great accuracy. As a medium game cartridge, the .223 is under powered if fast killing is to be expected with ordinary chest shots. The one exception is when using tumbling FMJ ammunition which completely and utterly changes the performance of this cartridge on medium game.
The tumbling 55 grain bullet is truly violent and fast killing and is the most effective medium game hunting load for the .223. Exit wounds on medium game are often as wide as 3”. However, it must be stated that when full metal jacket ammunition tumbles, the bullet also very gradually falls to pieces due to the unsealed base of the bullet allowing jacket core separation. Because the process is gradual, wounding occurs through vitals and bone, rather than on impact resulting in adequate penetration for all but tail on shots on medium game.
For many years all .223 caliber sporting rifles featured barrels with a twist rate of 1:12. Recently, some manufacturers have increased twist rates to 1:9. When 55 grain FMJ ammunition is used in either 1:12 or1:9 twist barrels, wound channels are extremely small, about 6mm in diameter with mild bruising around the wound (the former T44/7.62/.308 Winchester is no better in this respect). The one brand of 55 grain FMJ ammunition that does tumble is Norinco although the mechanism which initiates yaw on impact is difficult to ascertain.

In some cases, rifles with a 1:12 twist will produce tumbling on impact with 62 grain FMJ ammunition. The decision of whether a hunter can adopt such a load must be based on whether the rifle is capable of producing adequate accuracy. Many rifles can shoot around the 1MOA mark with 62 grain FMJ ammunition. A second factor is the stability of the load because in some cases, a projectile can be so carefully designed and engineered that it retains stability and fails to produce excessive yaw on impact despite an incorrect twist rate.
Hunters who wish to experiment with these loads are highly encouraged to do so but should first ascertain their barrel twist rate, either by studying the revolutions of a ram rod and cleaning patch or by consulting manufacturer’s data. The use of FMJ projectiles can be significantly more effective than any available sporting .223 load.

Bullet Weight Twist
40-Grain 1:12
55-Grain 1:9
62-Grain 1:8 or 1:7
77-Grain 1:7 or 1:8
80-Grain 1:7

Apart from the use of FMJ ammunition, hunters using the .223 on medium game will achieve best results with neck and head shots. Typical sporting loads with conventional soft point ammunition can penetrate through the chest walls of medium game but kills are always slow if the CNS is not destroyed. The .223 does not have the power to initiate hydrostatic shock. Using the .22 centerfires effectively on medium game requires a sound knowledge of game anatomy. Animals that are presented at awkward angles may have to be passed up until a better shot presents itself.