By now, thanks to television, movies, and video games, everyone under the sun knows of the 5.56x45mm NATO round. And yet, despite its prevalence, few outside of the firearms community know the various designations, like M193 and M855 — two military cartridges in use today. But you, the savvy firearm enthusiast you are, see the difference and are keen to learn more about M193 ballistics. We’re right there with you!

Civilian vs. Mil-Spec 5.56 Ammunition

First off, before we dive any further into the M193 ballistics, let us get one key distinction out of the way. As both the M193 and M855 are military cartridges, as we mentioned previously, strict regulations are surrounding civilian ownership of either round.

But thankfully, the firearms and ammunition industry created a workaround: nearly identical rounds to the military ammunition, but without the pesky “mil-spec” designation attached.

If you’re interested in buying M193 for your AR-15, look to Federal/American Eagle, as they have a commercial civilian option available under their XM line. The “X” in X193 shows the cartridge is meant for civilian use.

To confuse matters, a few ammunition manufacturers choose not to use the “X” designation but continue to label their rounds in the mil-spec standard method. These rounds do not pack the same punch as the military’s version, though they will get the job done.

M193/XM193 Design and Performance

M193 ammo cutaway view

Let’s start with the numbers. The M193 round is a 55-grain, boat-tail, lead core FMJ bullet with a muzzle velocity of, on average, 3,250 feet per second. To prevent moisture in the round, the primer and case mouth are both chemically sealed, which is crucial for military ammunition stored and used in harsh environments across the world.

We briefly mentioned the round’s introduction in the Vietnam War. Back then, it was a light, surprisingly fast bullet designed for the U.S. Army’s M16 — a firearm that features a slow rifling rate of 1:12. At the time, a 1:12 spin rate was more than enough for the M193 round, proving adequate compared to heavier rounds, such as tracers, while in combat scenarios.

But today, both the M16 and M4 variants feature a twist rate of 1:7, as do many civilian AR-15 rifles, or 1:9.

Regarding overall performance, the M193 round ensures fantastic accuracy and is well known for fracturing and causing significant flesh wounds against enemy combatants. At least, such results were expected at short ranges. Those within the military often complained about its stopping power at any distance, which is why much of the armed forces also adopted the M855 round.

External Ballistics of the M193

55-grain bullets are extremely fast

Most shooters focus their attention on the external ballistics of the M193, and rightfully so, too. It would be best if you considered the aerodynamics of any bullet leaving the barrel of your AR-15. For the M193, on a sunny day with little wind, the M193 will fly straight up to 225 yards. After that, you must account for bullet drop to land a hit on any target.

It’s often recommended to use a longer barrel to improve accuracy, which adds velocity thanks to angular momentum. Therefore, it’s safe to assume a rifle build with an extended barrel will prove useful with the M193 ammunition.

Regarding weight, the M193 is relatively light. It weighs 3.63 grams. As you likely know, the lower weight means more significant acceleration through the barrel which equates to greater velocity. We’re talking about a fast round here, at 3,250 feet per second. At such speeds, the M193 is quicker than most other 5.56x45mm variants.

M193 and Barrier Penetration

Along with many complaints regarding soft target penetration, active duty in Vietnam and beyond routinely complained about barrier penetration. Despite its prevalence in the military today, M193 failed to penetrate the likes of window panes, particular clothing objects, and even some vegetation forms, which proved difficult during Vietnam.

Why the categorical failures in combat zones? It’s said that M193’s shortcomings stem from its simplistic design and mass production. Further research has shown that, back during Vietnam, the original M16 and its twist rate of 1:12 that led to countless issues in the field.

In reality, M193 is a devastating round inside of 100 yards or so. It’s high velocity and light weight means that it is prone to tumbling and fragmenting when it enters flesh, and dumps it’s energy very quickly. However, in the dense jungles of Vietnam, the round also had trouble penetrating vegetation that did not affect larger caliber rounds as much.

Is M193 for Me?

Absolutely. M193 get’s a bad rap from it’s Vietnam days, and because it’s the cheapest of the 5.56 ammo available. But that doesn’t mean it’s bad. In fact, it’s undoubtedly the best training ammunition. And it still performs well enough on target that you can drop most animals you’ll run across, including nature’s deadliest predator. While you won’t be printing cloverleaf groups, you won’t have any problem hitting your target out to 400+ yards either. All in all, M193 has stood up to the test of time, and may not be the best for any role, but it’s certainly the best jack-of-all-trades.