M193 vs M855: Which 5.56 Round Should You Stockpile?

First Shots: M193 vs M855

You’ve already decided which rifle to purchase. Now you need to know which 5.56 ammo to feed it. M193 vs M855 (aka “green tip” ammo).

The M193 vs. M855 debate boils down to these points. M193 ammo is the better choice to buy in bulk, as it is less expensive and offers solid performance out to 500 yards. M855 green tip ammo offers better penetration and is slightly more accurate at longer distances. The M855 bullet also contains steel, and is therefore prohibited at many commercial gun ranges.

If you’re ready to load your mags with either of these amazing 5.56 cartridges, make sure to check out our bulk 5.56 ammo offerings. Otherwise, keep reading to learn why M193 ammo is my preferred choice.

Key Differences Between M855 and M193

M193 Ammo History

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The M193 cartridge was developed in the early 1960s. It was formally adopted by the U.S. military for its new M16 rifle in 1964.

Initially developed as the 223 Remington, the new military ammo was designed to fire a 55 grain full metal jacket (FMJ) boat tail projectile at a muzzle velocity of 3,250 fps, and have maximum chamber pressure of 55,000 psi.

The 223 Rem round was designated "Cartridge, 5.56mm ball, M193" upon its adoption in 1964.

The M193 saw its first action in the jungles of Vietnam. It remained our frontline battle cartridge until the late 1980s, when the military switched to M855 ammo (more on that in a moment).

The M193 cartridge is sealed at its case mouth and primer pocket for improved moisture resistance. The primer pocket is also metallically crimped in place to prevent primers from backing out (and potentially striking the shooter's eye) during automatic fire.

Early M16s had a relatively slow 1:12 barrel twist rate, which stabilizes a 55 grain bullet extremely well. In general, the M193 round is stabilized effectively in barrels ranging between a 1:9 to 1:12 twist rate, and reaches its full muzzle velocity potential from a 20" barrel.

M193 Specs

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One of the major benefits of the 55 grain projectile is its propensity to yaw and fragment when it encounters soft tissue. The bullet fragments inflict serious trauma whilst simultaneously mitigating the risk of over-penetration.

However, there are some downsides to the M193.

Bullet fragmentation was not always observed on the battlefield, with many soldiers reporting their bullets merely passing through enemy combatants. This presented a serious issue, as the M193 round's narrow projectile's terminal performance is significantly less injurious without fragmentation.

Another issue was the bullet's tendency to deflect when it encountered barriers like thick clothing or vegetation (I hear there's a lot of the latter in Vietnam). Overall, M193 is not very effective at penetrating barriers and is ineffective against modern body armor. This wouldn't have been a major problem while fighting unarmored Viet Cong soldiers, but modern militaries issue ballistic plates and helmets which the M193 is ill-equipped to handle.

This is where the M855 comes in.

M855 Ammo History

Tensions were high between the USSR and United States/NATO after the Vietnam War. Conflict seemed inevitable, which led the NATO alliance to sign a treaty replacing the 7.62x51mm (308 Winchester) with a smaller, lower-recoil cartridge in 1970.

FN Herstal took up the task of creating a new round, using the M193 as a starting point. What they developed came to be known as "M855" to the U.S., and "SS109" to other NATO members.

Often referred to as "green tip ammo," M855 bullets have bimetal cores: lead in back, steel in front. Their jacketed tips are painted green to facilitate identification by soldiers on the battlefield.

M855 ammo has been NATO and the U.S. military's primary intermediate combat cartridge since 1980. On paper, the M855 rounds sound like a massive upgrade over M193. However, battlefield reports from the First Gulf War and Somalia paint a different picture.

Soldiers on the front lines often reported M855 ammo being ineffective against enemy soldiers. This has been mostly attributed to the M855's inability to fragment when it impacts soft targets.

Although the M855 bullet's steel "penetrator" tip promotes more effective penetration through barriers, it was discovered that the bullet often passes straight through its target, inflicting a small wound channel as a result. Soldiers reported enemy combatants taking multiple shots of M855 and still not going down.

Those lackluster terminal ballistics sparked the development of a variety of new AR-15 cartridges during the early 2000s. The military eventually settled on the M855A1, which we will discuss in an upcoming section.

Green Tip Ammo Specs

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The M855 round fires a 62 grain FMJ boat tail projectile with a soft lead core and a 7 grain mild steel penetrator tip. Its muzzle velocity is slightly north of 3,000 fps, and it has a maximum chamber pressure of 62,366 psi (430 MPa).

The primer pockets and case mouths of M855 ammo are sealed, just as with M193 ammo.

The M855 bullet's hard steel tip increases its barrier potential for barrier penetration. The bullet also increases the M855 round's long-range capabilities – and not just because it is heavier.

The steel penetrator tip is designed to punch through a 0.135" mild steel plate at 500 yards (chosen to mimic Soviet-era ballistic helmets). Placement of the steel core also shifted the bullet's center of gravity toward its rear, thus improving in-flight stability and the potential for the tip to impact targets at longer ranges.

Its steel tip increases the bullet's length and therefore its ballistic coefficient. This also makes the M855 slightly more accurate at longer ranges. Note that faster twist rate barrels are needed to stabilize these longer, heavier bullets. A 1:7" twist rate is typically preferred for M855 ammo.

Can Civilians Own Mil-Spec M855 and M193 Ammo?

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Shooters often ask if they can own or purchase mil-spec ammo. The answer is “Kind of.”

As I’m sure you can imagine, there are some strict rules around what types of military ammo civilians can own and use.

However, this doesn’t mean civilians can’t get their hands on nearly identical ammo to what the military uses.

The Lake City Army Ammunition Plant often releases surplus ammo to the civilian market that was made on the same assembly lines as the military stuff. Federal also has its own version of M193, which it markets under its American Eagle label as “XM193.” (The “X” prefix merely designates that it was made for civilian use.)

To further complicate matters, some manufacturers (like PMC) often sell 5.56 ammo under the M193 and M855 designations, though it is not technically mil-spec.

M855 vs M193 Ballistics

One of the benefits of M855 ammo is its enhanced long-range shooting capabilities. But is the M855 really all that superior to the M193 in terms of ballistics? Let's take a look!

In the following ballistics table we compare M855 vs M193 ballistics fired from a 20" barrel out to 700 yards.

Both rounds are nearly identical in terms of bullet drop within 400 yards. It isn't until 500 yards and beyond that we see the M855 taking a slight lead over the M193.

At 500 yards, the M855 exhibits approximately -52" of bullet drop, while the M193 has dropped -54". It's not a massive difference, but the M855 does have the flatter trajectory overall.

At 700 yards, we see a larger disparity between the two rounds, with the M855 showing -140" of bullet drop compared to -156" for the M193.

The M855 also carries more kinetic energy to all ranges compared to the M193. However, this additional kinetic energy does not necessarily translate into enhanced combat effectiveness. If you recall, the main critique of the M855 is its tendency to over-penetrate and not fragment when it strikes a soft target.

This begs the question: Is M855 better than M193 from a ballistics perspective? From a numbers standpoint, yes, it is. The M855 clearly has a flatter trajectory and hits harder at range than the M193.

However, is the average shooter really going to notice any difference between the two? I'll go out on a limb and say they probably won't. The majority of shooters (myself included) will spend most of their time shooting between 100 and 500 yards. At those distances, both rounds are relatively identical in terms of performance.

M193 vs M855 for Self-Defense

Neither M193 nor M855 is ideal for self-defense.

In general, it is inadvisable to use full metal jacket (FMJ) ammo for home defense due to the higher risks of over-penetration and poor terminal ballistics.

However, if you only have M855 and M193 for home defense, then M193 would make the better choice. The round’s bullet has higher potential to cavitate and fragment, making it the better choice when barrier penetration is not needed.

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Can M855 Ammo defeat body armor? Is it Legal?

No: M855 ammo cannot defeat body armor. Although M855 ammo sounds like it should be armor-piercing with its steel penetrator insert, it is not designed to penetrate modern body armor.

It was developed primarily to be more efficient at barrier penetration than M193, and to defeat Soviet-era steel ballistic helmets. In general, M855 accomplished those goals, although there are some reports concerning the round’s inability to penetrate auto glass.

Regardless, the M855 cartridge does not satisfy the ATF’s definition of “armor piercing.” As such is completely legal for civilians to own.

A Quick Note on Nomenclature: 223 Remington vs 5.56 NATO

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Many new shooters might be confused about the differences between the 223 Remington and 5.56x45mm NATO cartridges. Some shooters will refer to them interchangeably, but this is a mistake.

Although the 223 Rem and 5.56 have virtually identical external dimensions, the two rounds are slightly different.

You can read more about those differences here: 223 vs 5.56.

In short, a 223 Rem can safely be fired from a firearm chambered in 5.56, although the opposite is not true.

M855 vs M193: Which Is Best for You?

Selecting the best ammo for your AR-15 really comes down to understanding what you want your rifle for.

In general, most shooters should stock up on M193 ammo. Although M193 is an older design, it still works perfectly fine. You can fire it at virtually any rifle range. It's also inexpensive and plentiful, and it performs well in most rifles.

M855 ammo is great for barrier penetration and long-range target shooting. Although this stuff won't punch through Level IV ballistic plates, it's always good to have some on hand for a Red Dawn-type scenario!

Although M855 is banned at many shooting ranges due to the steel contained by its bullet, some manufacturers like Hornady and Winchester offer 62 grain factory loads without penetrator tips. That lets you have all the benefits of shooting a heavier bullet without the target-destroying tendencies of classic M855 ammo.

It's good to have a stockpile of both types of ammo on hand for any liberty-infringement or SHTF situation you might encounter. If you're looking to increase your 5.56 ammo reserves, make sure to check out our 5.56 bulk ammo page for all the best deals on 5.56 NATO ammo we have in stock. Whichever military load you choose, make sure to stack it to the rafters!

Written by

Chris Dwulet