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Different Types of 5.56 Ammo

different types of 556 feature

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Hey all, we here at True Shot Ammo are going to go over different types of 5.56 ammo today. The 5.56 is one of the most common and widely used cartridges among law enforcement, military, and civilian users. It is only natural for there to a wide range of ammunition offerings suitable for various use cases and purposes. Our goal with this blog post is to cover a variety of the popular 5.56 ammunition offerings while going over their traits, features, and more. Without further ado, let’s talk about different types of 5.56 ammo.


What is 5.56?

The 5.56 is an iconic military caliber which is employed by many countries in military and law enforcement capacities. The official designation for the cartridge is 5.56x45mm NATO and is also typically referred to as 5.56 NATO or simply 5.56. The use of any of these terms makes it obvious that you are talking about 5.56 ammo and the cartridge in general.

The 5.56x45mm NATO’s roots can be traced to the .223 Remington cartridge, a popular smallbore sporting cartridge. Initially development for the cartridge began in the United States in 1957 alongside efforts to develop a smallbore, high velocity firearm. This would eventually lead to the introduction of the AR-15 and subsequent M-16 series of rifles. The cartridge would go on to see use by American forces in the Vietnam War and subsequent conflicts. During the 1970s and 1980s, NATO expressed interest in a standardized, smallbore cartridge to replace the 7.62x51mm NATO round. This led to the cartridge’s adoption by NATO in the form of the SS109 cartridge. After its adoption, the round has seen use with NATO members and allies such as the United Kingdom, Austria, France, and even Japan.

While originally intended for use in auto-loading rifles and carbines, the cartridge has been utilized in a variety of other firearms. Bolt action rifles are commonly found in the 5.56x45mm NATO round in addition to a few lever action rifles. The high velocity and light recoil of the cartridge can be appreciated in a multitude of platforms.

Civilian shooters of all types enjoy the 5.56x45mm NATO cartridge, particularly when used in an AR. The light recoil of the cartridge can be felt in both manual action and autoloading firearms, making it a comfortable round to shoot out for various firearms. This means that novice shooters and experienced shooters alike can effectively utilize the cartridge. The round is particularly well-suited to instructing new shooters as they are exposed to a versatile and effective centerfire round which doesn’t boast the stout recoil of something like a .308 Winchester.

5.56x45mm 77 Grain OTM from Black Hills - optimal for a 1:7 twist barrel.
5.56x45mm 77 Grain OTM from Black Hills - optimal for a 1:7 twist barrel.

“M” vs “XM” Designations

Before we delve into a further discussion of 5.56 ammunition, it is important to cover the difference between “M” and “XM” designations. These designations can be found in the name of a particular loading, such as M193 and XM193. The “M” prefix denotes the fact that the loading has been loaded to military specifications and passed testing needed to bear the designation. Practices such as sealing casings and staking primers are common in addition to ensuring consistent performance which aligns with loading specifications. The “XM” designation refers to loadings which simply do not meet military specifications. This can be because they were not tested or there were variances in the loadings which kept them from meeting military specifications.

While “XM” 5.56 ammo offerings do not meet military specifications, they are still worth considering, especially for plinking and training purposes. Most shooters won’t even be able to tell the difference between the loadings in most cases, especially when shooting. Some extreme examples may be more noticeable and feature distinct differences in terms of velocity and recoil impulse. Some loadings may be lighter than others in some cases. All in all, both “M” and “XM” designated ammo are viable for use as far as 5.56 ammo goes.



The M193 loading is one of the most common and plentiful 5.56 loadings one will encounter on the market. This 5.56 ammo offering will feature a 55 grain lead core projectile of the full metal jacket variety. Due to the lighter weight of the projectile, this loading will typically feature velocities which generally lie between 3,000 – 3,300 feet per second (FPS). Of course, velocity is also determined things such as barrel length and altitude.

The lead core nature of these rounds makes them safe for use at both indoor and outdoor ranges. Simply put, these loadings lack any steel which can potentially damage a backstop or create sparks. Due to the fact that these loadings are range safe, they are well-suited for training and practice. The fact that 5.56 ammo of this type is common and plentiful also aids in making this round well-suited to training and plinking use.



The M855/XM855 loadings set themselves apart from other 5.56 ammunition offerings due to their iconic green painted tips. Due to this green paint, these loadings are often referred to as “green tips.” The loadings feature 62 grain FMJ projectiles which constitute a lead alloy and steel core. This steel core is often referred to as a steel penetrator or as what makes the M855/XM855 a “light armor penetrator” round. Despite these names, the cartridge is not classified as an armor piercing round. M855/XM855 loadings will generally feature velocities between 2,700 – 3,000 FPS, ultimately depending on barrel length and altitude.

The presence of the steel core in these loadings leads to them being prohibited at most indoor and outdoor ranges. Indoor ranges cite the fact that the loading and other steel core offerings can potentially damage the rubber backstops used at most facilities of this type. Outdoor ranges will often bar the use of M855/XM855 ammo due to the fact that steel projectiles can potentially generate sparks when they hit steel targets or rocks. This can potentially lead to fires in some cases.



SS109 5.56 ammo offerings are similar to M855 loadings and feature the same style projectile. While the two loadings feature the same type of projectile, SS109 and M855 type loadings are distinct. A distinct difference between the SS109 and M855 loading is the absence of a painted green tip. This is because the iconic green tip found on M855/XM855 loadings is present due to United States military specifications. The SS109 originated in Belgium and serves as the basis for a NATO adopted loading and notably never featured a green tip. At its core, the SS109 loading is a FMJ 62 grain offering which, like the M855/XM855, features a steel core. Due to the inclusion of a steel core, the SS109 may be barred from use at certain indoor and outdoor ranges due to the same reasons as M855/XM855.



The Mk262 is a popular 5.56 ammo loading which is optimized for precision work. The loading was developed by Black Hills Ammunition at the request of the United States Navy in 1999. Since this initial loading and its subsequent adoption, the original company and others offer Mk262 loadings (and imitations) for commercial use. Black Hills Mk262 loadings are held to high accuracy standards – ten groups of ten shots at distances of 300 yards. The company will not ship 5.56 ammo of this type unless it is capable of producing sub 2” groups (.64 MOA maximum). The loading is optimal for use in issued rifles such as the Mk12 designated marksman rifle and the Mk18 CQBR due to its heavy 77 grain projectile.

Due to the heavy projectile, the Mk262 loading pairs great with 5.56 rifles that feature 1:7 twist rates. Rifles with 1:7 twist rates have faster twist rates than their 1:8 and 1:9 counterparts and are capable of stabilizing heavy projectiles such as this 77 grain offering. With an optimized rifle and this loading, one can effectively stretch a 5.56 rifle out to extended ranges. Competition and precision-oriented builds and Mk12 style clones are well-suited for this loading in addition to short-barreled rifles.

PMC M855 Green Tip Ammo
PMC M855 Green Tip Ammo

Who Makes 5.56 Ammo?

Currently, 5.56 ammunition is produced by a number of companies. These ammunition manufacturers are located in a variety of countries across the globe, producing ammo for both commercial and professional use. Companies such as PMC, Black Hills Ammunition, GGG, Norma, Winchester, and Aguila are among some of the manufacturers of 5.56 ammo. These producers are just a drop in the bucket when it comes to companies who produce 5.56 ammunition for sale. In addition to standard FMJ loadings, many purpose built 5.56 ammo offerings are produced for uses such as hunting, self-defense, and match use.



All in all, there is a wide variety of 5.56 ammunition being produced today. These loadings can easily be found in individual and bulk 5.56 ammo offerings, often in the form of cases and ammo cans. We here at True Shot Ammo carry a wide variety of ammunition, specifically 5.56 ammo. Whether you are looking for plinking, training, self-defense, or hunting, we have got you covered. Beyond 5.56 ammo, we also have a wide variety of other ammunition for sale such as .223 Remington, 9mm Luger, and 12 gauge for your other shooting needs. As always, happy shooting.


Need bulk ammo? At True Shot Ammo, we have a wide variety of handgun ammo and rifle ammo available to purchase. Please visit our website, call us at (888) 736-6587, or you can email us at [email protected] for more ammo options.


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