M855 vs M193: Which 5.56 NATO Round is Best for Your AR-15?

The AR-15 has become a staple in the firearm community, not only because of its modular design but also because it can adapt to different ammunition types.

Among the popular 5.56 NATO rounds, the M855 and M193 stand out due to their widespread use, affordability, and performance in various scenarios. Whether you’re a competitive shooter, a tactical enthusiast, or someone focused on home defense, understanding the differences between these two rounds is critical to optimizing your rifle’s performance.

In this article, we’ll break down the key differences between the M855 and M193, covering aspects like accuracy, penetration, cost, and real-world applications to help you decide the best fit for your needs.

Purpose and Design

When comparing the M855 and M193, starting with their intended purpose and design is essential. Both are classified as Full Metal Jacket (FMJ) rounds, but each was designed with specific goals in mind.

• M193: This 55-grain round was originally developed during the Vietnam War era for use in the M16 rifle. The primary goal behind its design was to create a lightweight, high-velocity round that could deliver reliable terminal ballistics in combat. Upon impact, the M193 tends to fragment, increasing its lethality at short to medium ranges. This makes it ideal for civilian use, self-defense, and scenarios where quick stopping power is critical.
• M855: Commonly referred to as “green tip” ammunition due to its green-painted steel penetrator tip, the M855 is heavier at 62 grains. Developed for military applications, the M855 was designed to improve penetration, especially against light armor or barriers. The steel core allows it to punch through materials like car doors, thin metal, and glass more effectively than the M193, but it can sometimes over-penetrate when used on soft targets, reducing its immediate stopping power.

In summary, the M193 is better suited for engagements where fragmentation and stopping power at shorter distances are needed. At the same time, the M855 excels in scenarios requiring penetration through barriers or long-range accuracy.

Performance and Accuracy

Regarding performance and accuracy, the differences between M855 and M193 become even more apparent. Both rounds are capable, but their performance varies depending on range, target type, and the twist rate of your AR-15 barrel.

• M193: Known for its lighter 55-grain bullet, the M193 generally achieves higher muzzle velocity, often around 3,200 feet per second (fps) from a 20-inch barrel. This makes it more effective at short to medium ranges, where speed and fragmentation lead to larger wound cavities and quicker incapacitation of soft targets. Accuracy-wise, the M193 excels at distances up to 300 meters. However, the lighter bullet can be more prone to wind drift at longer ranges, making it less stable than the heavier M855.
• M855: Weighing 62 grains, the M855 has a lower muzzle velocity—around 3,000 fps—but compensates with a higher ballistic coefficient. This gives it a flatter trajectory and less bullet drop at longer distances, making it more suitable for engagements beyond 300 meters. Additionally, the steel core improves its penetration through barriers such as glass, light metal, and dense foliage, making it effective in tactical or military scenarios. However, this same penetrative ability makes it less ideal for self-defense, as it may over-penetrate soft targets, potentially reducing immediate lethality.

The barrel twist rate of your AR-15 plays a crucial role in accuracy. The M193 performs best with a slower twist rate, such as 1:12, the standard in early M16 rifles. On the other hand, the M855 is optimized for faster twist rates, such as 1:7 or 1:8, which stabilize the heavier bullet for greater accuracy at longer ranges.

Usage Scenarios

The M855 and M193 rounds each excel in specific use cases. Choosing the right round for your needs depends largely on how you intend to use your AR-15, your environment, and your shooting goals.

• M193: This round is highly favored for civilian use, including self-defense, target shooting, and training. Its ability to fragment upon impact makes it particularly effective at incapacitating threats at close to medium range, especially on soft targets like home intruders. Since the M193 is less likely to over-penetrate barriers such as drywall or furniture, it is often considered a safer option for home defense. Its affordability and widespread availability make it an excellent choice for general training, allowing shooters to stock up on practice rounds without breaking the bank.
• M855: The M855, with its steel penetrator tip, is a favorite among military and law enforcement professionals, especially when shooting through barriers like car doors, glass, or light armor is necessary. Its heavier design and increased stability at long ranges make it a popular choice for long-range shooting and tactical engagements. However, its tendency to over-penetrate soft targets means it might not be the best option for self-defense in urban environments, where the risk of hitting unintended targets is higher. That said, for rural shooters or those using their AR-15 in more open areas, the M855’s ability to punch through light barriers makes it an ideal choice for applications like a truck gun or in survival situations where reliability and barrier penetration are critical.

In essence, the M193 is better suited for short-range engagements and scenarios where fragmentation and rapid incapacitation are needed. At the same time, the M855 shines in situations where barrier penetration and long-range accuracy are priorities.

Cost and Availability

One key factor in choosing between M855 and M193 is cost and availability. Both rounds are widely available and relatively affordable compared to other types of 5.56 NATO ammunition, but there are some distinctions to consider.

• M193: Generally, M193 tends to be slightly cheaper than M855. This is primarily because manufacturing is less complex, with no steel penetrator core. For those looking to stock up on ammunition for training or target practice, M193 is often the more economical option. Furthermore, its availability is widespread, and it is commonly found at both local gun shops and major online retailers. The simplicity of its design makes it a go-to for many civilian shooters who prioritize affordability.
• M855: Although still reasonably priced, M855 rounds tend to be slightly more expensive due to their more intricate design and the inclusion of the steel core. Because of its military applications, M855 is subject to greater demand from professionals, which can sometimes lead to fluctuations in price. Moreover, certain ranges may restrict the use of green tip ammo, limiting where you can shoot this round. Despite this, M855 is still widely available and remains a popular choice for those who require its enhanced barrier penetration and long-range performance.

Conclusion

Ultimately, your choice between M855 and M193 will depend on your specific needs and the scenarios in which you intend to use your AR-15.

• M193 is the better option for self-defense, target shooting, and short-range engagements. It offers effective fragmentation upon impact and minimal over-penetration. It is also a more cost-effective choice for those who need to buy in bulk for training.
• On the other hand, M855 excels in long-range shooting and tactical situations where barrier penetration is critical. Its heavier weight and steel core provide better stability at longer distances and allow it to punch through light obstacles that would stop the M193.

In summary, both rounds have their strengths, and the choice comes down to your specific use case. Whether you’re a civilian looking for affordable practice rounds or a tactical shooter seeking penetration power, understanding the differences between M855 and M193 will help you make the right decision for your AR-15 setup.