.223 (5.56 x 45)
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High Velocity, Lightweight Bullets for Use in a Lightweight Rifle
Thanks to Uncle Sam (specifically the US Military), the .223 has become one of the most common rounds in the world. It's not as common as the 22LR and may not be as widely known as the 7.62x39 from the infamous AK47 rifle, but nevertheless the 223 round is extensively used around the world in modern semi-automatic rifles. It all started back in the late 1950's when some leaders in the US military were seeking a lighter recoiling round to replace the 7.62x51 used in the M14 rifles that were standard issue at that time. Some believed that the powerful 7.62x51 round fired in the M-14 had too much recoil for rapid fire or full auto operation. They wanted a different rifle that would fire a lighter recoiling bullet which would make it easier to control and to keep the gun on target. Eugene Stoner from Armalite was involved in the development of the AR-10 which also fired the 7.62 NATO round, and he was approached with the idea of creating a scaled down version of the AR10 which could fire a lighter round. The result was the AR15 rifle and the round chosen was based on the .222 Remington that was already being used in commercially sold bolt action rifles. The problem with the 222 was that the case geometry was not ideal for semi-automatic operation. It was felt that the angle of the case neck was too abrupt for reliable feeding and extraction in a semi-auto rifle. The solution was to increase the overall length of the case and change the neck angle, and that's how the .223 Remington round was born. This round is also commonly known as the 5.56 NATO or more specifically the 5.56x45mm round. The AR-15 developed by Armalite met the requirement of being an easy to fire rifle with the light recoil of the 223 round. Colt bought the rights to produce the AR15 from Armalite, and the Colt M16A1 was produced. This new rifle saw limited use in the military in the early 1960's in Vietnam, and later in the Vietnam war the M-16 was used widely. By 1970, the M16 had become the standard issue US military rifle. It is still in service in the US military and armed forces around the world to this day.
Colt M16A1 Rifle
Early on, there were some problems in the field with this new rifle, and it was not uncommon for the M16A1 to jam. In the heat of battle, this could be a death sentence for a solider holding the malfunctioning M-16 rifle. Unfortunately, it was in fact reported to have been responsible for the deaths of soldiers killed by the North Vietnamese's more reliable AK47's. Tragically, US soldiers were found dead next to their disassembled M16's which were taken apart in the soldier's desperate attempt to fix the malfunctioning rifle. Thankfully changes were made to the gun, the ammunition, and also in the training of military personnel in the proper cleaning and maintenance of the M16. After this rocky start to the M16's service, the gun proved itself to be reliable if properly maintained, and it was also more accurate than the AK47. Today, the AR15 is the semi-auto version of the M16 and it is produced by a large number of different manufacturers. The AR-15 is available for purchase by civilians and by law enforcement personnel.
Colt AR15 Rifle
After covering some background on the firearm that was designed to shoot the .223 round, let's get back to some more details on the 5.56x45 round itself. With such a lightweight bullet, it would seem that it might not be as effective as a heavier, more powerful bullet. As it turns out, the .223 turned out to be a surprisingly effective bullet given its modest ballistic specs. Traveling at around 3,200 fps, the M193's small 55 grain bullet could produce a maximum of around 1,300 ft-lbs of energy. In comparison, the larger 7.62 NATO bullet weighs nearly 3X as much, and the 7.62 generates ballistic energy levels that are TWICE as much as the smaller 5.56. With that information, one might think that the 5.56 is a much less effective bullet; however, numbers and ballistic specifications don't always give the full picture. True, the lightweight 223 bullet is more prone to being deflected or knocked off course by barriers. In fact, the high speed 5.56 bullet will commonly fragment upon impact with barriers. This can result in poor performance when soldiers are engaged in a firefight with enemies that are hiding behind cover. Ironically, this lightweight bullet that easily fragments is also one of the reasons why the 223 round has proven itself effective in military service. Battlefield use has shown the 55 grain M193 bullet to have devastating terminal effects. When the M193 FMJ bullet strikes flesh at high velocities, the bullet begins to tumble. As the bullet is traveling sideways through a denser media such as flesh, the bullet will tear itself apart and fragment if the velocity is still high enough. At longer ranges, it is possible that the velocity may drop enough so that the bullet may not fragment, but most distances found in battle are close enough to ensure high velocity fragmentation. The thin metal jacket of the bullet is designed to allow the bullet to fragment. The result is a wound channel that is much bigger than might otherwise be expected from such a tiny bullet. The results were so devastating that some thought the M193 was too destructive and inhumane to be used in battle. The video below shows the M193 being shot into ballistic gelatin, and it illustrates how this lightweight bullet tumbles and fragments. Notice that the largest piece of the bullet exits this relatively small 10" gel block.
The US military has largely moved away from the M193 and switched to heavier rounds like the 62gr M855 which is less prone to fragmenting so violently. Unfortunately for soldiers in battle, this also means that the M855 may not be as effective in stopping enemy forces. In fact, it has been reported from the battlefield that the M855 has not always been effective in quickly stopping enemy threats. The M855 is also longer than you'd expect just based on the increased bullet weight along. The M855 has a steel core in front of the lead base. This is all enclosed by the metal jacket. The overall bullet length is longer and requires a different barrel rifling twist rate in order for the bullet to be stabilized properly. Because of the inconsistent performance of the M855, the US military adopted the newly designed M855A1. This new bullet design has an exposed steel penetrator tip that is backed by a copper core at the base instead of the lead core of the normal M855. Not only has the new round proven more effective in soft targets, but it has also proven more effective in penetrating barriers such as steel and concrete. The picture below was taken by a gun enthusiast and is a good visual comparison of the 3 different bullets that have been mentioned here.
M193 55gr - M855 62gr - M855A1 62gr
Barrel Twist Rates
That brings up another topic of interest regarding the different 223 bullets. Depending on the rate of twist of the barrel rifling, some bullets may not be stabilized properly and accuracy will be affected. Some of the very earliest AR15/M16 rifles were produced with a 1:14 twist. That means that the rifling would twist a full rotation in 14 inches. That is a very slow twist rate and it does not spin the bullet as fast. This 1:14 twist rate was selected because that was what was commonly found in .222 bolt action rifles at the time. The M-16 barrel twist rate was later changed to 1:12 which worked very well for the M193 55gr bullets that were standard issue at the time. Later, when the M855 was introduced along with some other bullets, the 1:12 rate was found to be inadequate to properly stabilize these different bullets. As a result, the rifling was changed to a faster 1:7 rate which was able to provide the faster spin needed to keep the heavier and longer bullets in a proper flight path; however, now this faster rate was not a good match for the lighter & shorter M193 bullet. Since the US military was largely moving away from the M193 anyway, then this did not matter so much. In civilian AR15 rifles, the twist rate is very commonly chosen to be 1:9. This provides a good compromise that enables these rifles to shoot a variety of different bullets accurately. Some say that a 1:9 barrel can properly stabilize bullets ranging from around 45 - 75 grains, but there is some variation depending on the particular barrel and also the different bullets. It would probably be safe to say that a 1:9 twist should be good for bullets in the 50-70 gr range, which makes the 1:9 rifling a very versatile choice. The Ruger Mini-14 is another popular rifle that shoots the 5.56/223 round. Depending on when it was manufactured, the Mini-14's came with twist rates including 1:10, 1:7, and most recently the more popular 1:9 rate.
223 vs 5.56
It should be stated that technically the 223 is not identical to the 5.56 NATO round. The 5.56 is usually loaded to higher velocities with higher chamber pressures. In addition, the chambers machined in barrels specifically made for the 5.56 NATO round have slightly different chamber geometry than the SAAMI spec 223 chamber. In the end, what this means is that guns with chambers specifically made to the 223 specs should not shoot the 5.56 round. On the other hand, chambers made for the 5.56 round can shoot either the .223 or the 5.56 round safely. There should be markings on each gun that state if the gun was made for the 223 or the 5.56. If it specifies 223, then the hotter NATO ammunition should be avoided. One gun that sort of confuses the issue is the Mini-14 which typically has .223 stamped on the receiver, but Ruger states that either the 5.56 or the 223 can be shot. This means that the chamber is not a 223-only configuration. One exception to this is the Mini-14 Target rifle which does have a 223-only chamber.
Because of the popularity of the 223 round, there is a large variety of different bullets available ranging anywhere from a hyper-velocity 35gr bullet pushing 4,000 fps all the way up to a heavy subsonic 100gr bullet. As mentioned earlier, the rifling twist rate will largely determine which bullet can be accurately shot out of each barrel. If you've got a rifle with the 1:9 rifling, then you can probably shot most of in the intermediate weight bullets (50-70gr) with good success. If you have something with the 1:10 to 1:12 rate, then you probably will need to stick with the lighters bullets that are 55gr or less. If you have a 1:7 twist, then you will need to stick with the heavier bullets. One note regarding the super lightweight, high velocity rounds such as the 35-45 grain bullets. These high velocity rounds will result in more barrel wear. In other words, you will shoot out the inside of the barrel (rifling) quicker if you use these high velocity rounds extensively. Ultra high velocities are hard on a barrel especially in a semi-automatic rifle that can shoot a lot of bullets at a high rate of fire.
Hornady NTX 223 35gr Bullet with Polymer Tip
Not only are there a variety of different bullet weight to choose from, but there are also a number of different bullet designs available including Fully Metal Jacket (FMJ), Hollow Point (HP), Soft Point (SP), and Polymer Tip (POLY). First of all, just as the name implies, the standard Full Metal Jacket (FMJ) style bullet is fully encased in a copper alloy jacket. A FMJ bullet, sometimes referred to as Ball ammo, will often zip right through things without any expansion or fragmentation. Some exceptions include the M193 and M855 rounds which are designed with a thin metal jacket with a cannelure which makes these bullets much more likely to fragment and create a much larger wound channel than would normally be possible with a FMJ bullet. Hollow point .223 bullets have a small HP in the tip that helps ensure more consistent fragmentation. In handgun bullets, a hollow point will usually result in expansion of the bullet, but with these ultra high velocity bullets the tiny HP usually results in fragmentation. Next, the Soft Point (SP) type bullet has an soft exposed lead tip that is designed to cause the bullet to mushroom and expand upon impact. Just as with the HP type 223 bullets, it's possible for a SP bullet to fragment if the velocity is high enough. In addition to the velocity of the bullet when it impacts the target, a lot of it will depend on the thickness and strength of the bullet jacket as to whether or not the bullet holds together. Typically, a properly designed SP will be have a strong enough jacket to hold the bullet together. Finally, some other 223 bullets have a polymer (plastic) tip which is inserted into a hollow point. This pointed ballistic polymer tip pushes into the hollow point upon impact and causes the bullet to violently fragment. These type of polymer tip bullets are usually marketed as varmint rounds, because they are not designed to penetrate deeply, but rather to fragment and dump all their energy into a relatively shallow wound. This works well for varmints because if the bullet penetrated too far, it would likely punch right through the small animal. The polymer tip bullets usually have a better ballistic coefficient because they are more aerodynamic and slice through the air more easily. They also are less prone to wind drift and they have a flatter trajectory. Of the 4 different types of 223 bullets, the FMJ will usually have the deepest penetration. Next in terms of penetration would probably be the soft point bullet with it's expanding bullet that holds together in one piece and the retained weight results in deeper penetration. It is possible that a SP bullet could penetrate deeper than a FMJ bullet if the FMJ quickly fragmented into tiny pieces which did not penetrate as far. The next round would probably be the hollow point in terms of penetration and then the polymer tip bullets with the least penetration. These are just generalizations and will depend on the specific bullet construction and the velocities upon impact. One final note on hollow point bullets, contrary to what might seem intuitive, a HP bullet is often more accurate than a comparable FMJ bullet. One reason for this is because a hollow point bullet is lighter in front (because of the HP cavity), and it has more of its weight in the back of the bullet. This weight distribution can help to better stabilize the HP bullet in flight resulting in a more accurate bullet.
There are so many different types of 223 (5.56x45) ammunition that it's hard to make one single recommendation. It really depends on the type of rifle that you have, what the barrel rifling twist rate is, and what is your intended use of the gun. If there could only be a single recommendation made, then it would probably be the Federal M193 55gr FMJ bullet. This bullet has been around for a very long time and it has proven itself on the battlefield. Because of the 55gr bullet weight, the M193 works well in virtually any rifle regardless of twist rate. Below is a picture of a M193 round and you will see the discoloration around the neck where the case was annealed. In most commercially sold ammunition, the cases are polished after annealing, so this discoloration is not visible. This is just being mentioned so it's clear that this discoloration is not a problem. It just means that this military ammunition is all business and focused more on performance and functionality than it is on cosmetics.
Federal M193 5.56x45 55 grain
Another benefit of the M193 is that it is usually less expensive than many other 5.56 ammunition choices. The combination of all these factors makes the M193 a good all around choice. Different companies manufacture M193 ammunition, but if you are looking to buy some, then it is advisable to get the Federal M193 made in the Lake City factory. The reason for this is because some of the other M193 ammo made by other factories may not meet military specs. What this means is that important factors such as jacket material and thickness might not be correct. Furthermore, other types of loads might not be loaded as hot which would result in lower bullet velocities and lower performance. If you want to ensure that you are getting the best M193, then try to be sure that it is being sold by Federal and was produced in the Lake City factory. Be aware that there are many different designations given for the Federal M193 ammunition. You might find this bullet sold under the following product numbers: M193, XM193, XM193BK, XM193CBP, XM193C, XM193F, XM193BL, XM193J, XM193A, XM193AF. These designations are all the same ammunition but they are simply packaged in different configurations. Some might be packaged in boxes of 20, some might be on stripper clips, and some might be bulk packaged loose in boxes of 1000. These are just some examples. Each product number listed just denotes a different type of packaging; however, all these should contain the same M193 bullet. If you are unable to find any of the Federal M193 ammunition, then another possibility is the Israel Military Industries (IMI) M193. This also has a good track record and is loaded to the hotter NATO specs. While on the topic of good alternatives, some people also like the Winchester Q3131 round which is basically Winchester's version of the M193. Generally, people have had good experiences with this ammo but it appears to be loaded to slightly lower velocities, but it is still very close to M193 specs. The Winchester Q3131A version is said to be produced in Israel at the IMI factory. Federal also markets some of their ammunition under the American Eagle name, and the AE223 series will often use the same M193 projectile, but they are typically not loaded as hot. The AE223 ammunition is loaded to the 223 SAAMI specifications and so you can expect bullet velocities to be around 100 fps less than the 5.56 spec Federal M193 ammo.
On another note, a round like the M855A1 would be better when shooting at longer ranges and also for penetrating barriers, but this bullet requires a twist rate that is suitable for this longer and heavier projectile. If for some reason a person does not want to use the M193, then there are many different types of 223 (5.56) ammunition to choose. Just stay away from the Russian made 5.56 ammunition such as Tula and Wolf because they have steel cases and will usually also have steel jacketed bullets with copper plating. Not only will these steel bullet jackets not behave the same as a copper alloy jacket, but they can also lead to accelerated wear of your barrel. In addition, the steel cases can cause more chamber wear and the lacquer coating sometimes used on the steel cases can also gum up the chamber and cause malfunctions. So, if you are looking for .223/ 5.56 ammunition, stick with good quality brass cased ammunition and consider military spec ammo such as the Federal M193.