M855 vs M193 Face-off: Which 5.56mm Round Dominates?

The AR-15, America’s most beloved rifle, excels in versatility and performance. Known for its lightweight frame and precise shooting, the AR-15 can be configured as a rifle, carbine, or pistol due to its modular design. This adaptability extends to ammunition compatibility, with the AR-15 handling everything from 40-grain rounds ideal for small game to 77-grain cartridges perfect for use with suppressors.

Amidst the resurgence of pistol-caliber carbines, the AR-15 continues to stand out. While 9mm rounds gain only a slight increase in power from longer barrels—often losing velocity due to optimal powder charges for shorter barrels—the AR-15 leverages the power of the 5.56/223 Remington cartridge. Decades of field use and modern ballistics testing affirm the 5.56 round’s efficacy as a potent man-stopper.

In today’s comparison, we get into two popular types of 5.56mm ammunition: the 62-grain M855 and the 55-grain M193. Join us as we explore which round offers superior performance for the AR-15 platform.

Origins of M855 and M193

The development of modern ammunition is often intertwined with the needs of military forces and the technological advancements of their times.

M855 is often referred to as green tip ammo for its special color coding (the projectile itself is painted green at the tip). These 5.56 cartridges push a 62-grain bullet designed with a boat tail, lead core, and a special steel "penetrator" tip. The specified muzzle velocity of M855 ammo is roughly 3,020 feet per second depending on the manufacturer. The primer and case mouth are chemically sealed, just like M193 ammunition.

Heavier and slightly slower, the M855 is a 62-grain 5.56×45 caliber bullet traveling around 3,000fps at the muzzle. The green-tipped M855 comes loaded with an 80% lead core and topped off with a 7-grain steel tip which provides the M855 with far superior penetration when compared to the M193 round.

Even though it’s slower due to the slight increase in bullet weight, the M855 actually sports a higher ballistic coefficient because of its increased length, allowing it to travel on a  flatter trajectory, with less drop, and it bucks the wind better at distance.

M193 was introduced during the Vietnam War era. Originally designed for the M16 rifle, its conception was driven by the need for a lightweight, high-velocity round that could be used in the automatic fire mode of the newly introduced M16. The M193 was meant to provide U.S. troops with better ballistics and performance than the 7.62x51mm NATO cartridge used in the M14 rifle.

M855 Ballistics vs M193

Although many have confused the M855 round to be armor-piercing, it is not. The steel "penetrator" at the tip of the core helps it punch through barriers pretty effectively though. It penetrates glass, thin gauge metal, thick clothing, and brush rather well.

However, don’t expect M855 rounds to plow through auto glass consistently, brick, or modern body armor. Infantry units in Iraq were reportedly frustrated that their Mil-Spec M855 ammo couldn’t penetrate windshields at shorter distances.

However, there are some instances of the M855 penetrating auto windshields without any issue whatsoever.

Because M855 ammo penetrates so well, it can wreak havoc on steel targets, which is why most indoor ranges, or outdoor ranges for that matter, do not allow you to shoot green tip ammo.

When it comes to performance on soft targets, M855 leaves a lot to be desired. The same characteristics that allow it to punch through barriers, also make it more likely to pass straight through a soft target without causing any significant tissue damage. The M193 round has an edge on M855 in this instance.

That special steel "penetrator" makes the M855 projectile a little longer than the M193. This extra length requires a faster twist rate for proper in-flight stabilization.

For this reason, M855 performs well in barrels with a faster 1:7 or 1:8 twist rate.

Given its lighter weight, the M193 often has a higher muzzle velocity, frequently recorded at around 3,150 feet per second (fps) from a 20-inch barrel.

Its lighter weight combined with the high velocity means the M193 has a flatter trajectory at closer ranges but might experience greater wind drift and less stability at longer distances.

The M193  round is best suited for barrels with a twist rate of 1:12 inches (one complete twist every 12 inches), which was the standard for early M16 rifles. This rate offers optimal stability for the lighter 55-grain bullet, ensuring accuracy over various distances.

What is M855 Ammo Good For?

So, if you’re shooting a rifle with a fast twist rate (1:7 or 1:8), choose M855 green tip ammo. Likewise, if you’re trying to poke holes through intermediate hard barriers, M855 green tip ammo is the way to go.

Does M855 Penetrate Body Armor?

One of the most common questions that get asked about M855 is whether it can penetrate body armor or not.

AP (Armor-Piercing) ammunition is designed to defeat ballistic armor intended to defeat conventional bullets. The GCA (Gun Control Act)  defines “armor piercing ammunition" as:

• A projectile or projectile core that may be used in a handgun and which is constructed entirely (excluding the presence of traces of other substances) from one or a combination of tungsten alloys, steel, iron, brass, bronze, beryllium copper, or depleted uranium; or
• A full jacketed projectile larger than .22 caliber designed and intended for use in a handgun and whose jacket has a weight of more than 25 percent of the total weight of the projectile.

Both parts of the above definition apply specifically to bullet construction and to their use in handguns. This goes back to the Law Enforcement Officer’s Safety Act which was intended to regulate “cop-killer" bullets from use in concealable handguns. M855 does not fall into the category or definition of armor-piercing ammunition.

That said, will M855 Defeat Body Armor? The short answer is no. M855 is not classified as an Armor Piercing round, neither literally nor by the BATFEs description of what an AP round is. It’s rated for use against light personnel and thin-skinned vehicles for military and law enforcement applications, and you’ll find it’s capable of punching through steel plates at the range, so don’t plan on shooting M855 at the gun range.

The M855 round was designed for peak ballistic performance out of a 20" barrel with a 1:9 twist. Originally it wasn’t created to defeat body armor but was meant to penetrate thin barriers such as car doors and steel helmets. It’s also good at bucking the wind at longer distances. The M855 bullet is 0.906" in length and is composed of a combination of lead and steel core with a partial copper jacket.

What Level Body Armor Stops 5.56 Green Tip?

To defeat the penetrating energy of a 5.56 round, one of the most common rounds in the US, would require, at minimum, Level III body armor, but that’s just standard 5.56, not M855 green tip.

Generally speaking, M855 can penetrate 3 mm of steel at a range of 600 meters. Fortunately, NIJ-Listed Level IV body armor is rated to stop at least 3 shots from an M855A1 round. The NIJ rates Level IV body armor as able to defeat armor-piercing bullets up to .30 caliber. Level IV body armor is going to be more expensive and heavier than Level 3 body armor, but it’s going to afford the best possible protection against M855 green tip ammo.

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Military and law enforcement officers typically will wear Level IV body armor for protection against 5.56 rounds including the M855. Not even M855 was designed to penetrate Level IV body armor. Thankfully, law-abiding civilians can buy Level IV armor today.

Is M855 Illegal? The Future of M855 Green Tip

The White House’s press people are denying it, but NSSF learned from Winchester Ammunition that they were being told that M855/SS109 ammunition sales to civilians from the Lake City, Mo., facility are on the chopping block.

That would potentially choke off over 30 percent of the ammunition used on AR-15 rifles by law-abiding citizens.

It would also risk the jobs of up to 500 employees and the Defense Department’s ability to surge ammunition production during increased operational tempo periods. Get it while you can!

Where Can I Buy M855?

What is M193?

The M193 is essentially the standard, average, or ‘run of the mill’ 5.56 ammunition that most purchase. Used in massive quantities by our military; the M193 is a 55 grain, lead-cored, full metal jacket round with a muzzle velocity of roughly 3,200 fps depending on the manufacturer.

What do these characteristics mean? They mean that this lightweight bullet is flying extremely fast, and is generally unstable (tumbling) when it makes contact with a target. This tumbling effect leads to a larger wound cavity, and ultimately, better lethality.

Known to be prone to fragmentation upon contact with a target, the M193 was not made to penetrate any sort of barrier, armor, or hardened material.

Some notable advantages of M193:

• Less expensive to use for training and practice
• Generally easier to get ahold of than M855
• Hunters prefer its terminal effects at short distances
• The round can be stabilized with most barrel twist rates

M193 Ballistics

Although M193 is an FMJ round, it often fragments inside soft tissue, creating a considerable wound channel. However, when it fails to fragment, M193 produces only minimal less-lethal wounds.

Many Vietnam Veterans complained about the M193. Claiming it had no significant effects on the enemies they shot at and hit. M193 also performs poorly when it comes to punching through soft barriers such as heavy clothing and thick vegetation.

If your rifle has a slower twist rate (1:9, 1:10, or even 1:12), M193 will yield better results.

M193 is more effective on soft targets that aren’t hiding behind a barrier, especially on targets 100 yards and in.

Where Can I Buy M193?

Is M855 or M193 Better?

You’re probably thinking that "penetrator rounds" or even “green tip ammunition" sounds pretty badass. And the fact that it penetrates through barriers means that you MUST have it.

In reality, M193 does a better job against soft targets within 100 yards since it tumbles and fragments vs the M855 which has the steel core.  Out past 100 yards, the M855 seems to catch up.

Keep in mind that the twist rate of your barrel will also affect how well the heavier M855 round performs.

If your barrel has a 1:7 or 1:8 twist rate, you’re good to go with M855, but if you have the more popular 1:9 twist rate such as I do, you’re better off running with the M193 ammunition.

Lastly, there will be a difference in price.  Most likely you’re going to see M193 slightly cheaper than M855, but nothing too crazy.

Which Round is Right For You?

Selecting the right 5.56/223 ammunition for your carbine, whether for home defense or as a practical truck gun, depends significantly on your environment and specific needs. For those in rural areas or for anyone using their carbine as a truck gun, a load with deep penetration such as the M855 is preferable. Enhanced penetration is crucial for potentially overcoming light barriers and ensuring safety without the risk of over-penetration in sparsely populated areas.

Conversely, urban dwellers should consider lighter, 50- to 60-grain soft point or hollow point rounds for home defense. Reputable manufacturers like HOP Munitions offer dependable options, including their 55-grain FMJ and 62-grain FMJ rounds, known for flawless performance. The AAC 55-grain Sabre Blade Black Tip soft point is also worth considering for its effective stopping power and safety in dense environments.

For training purposes and as a reliable backup, stocking up on M193 FMJ is advisable. Then work on beefing up your supply of preferred defensive ammunition. In these unpredictable times, being well-prepared with a reliable 5.56 carbine, ample ammunition, and high-quality magazines is not just practical—it’s essential for your safety and readiness.