Best 5.56 Ammo for Defense, Hunting & Bulk Purchase

History of the 5.56 NATO

In the 50s, the US Army outlined the requirement for the cartridge to be used in the future lightweight small-caliber rifle that would become a new standard-issue combat rifle for the military. In particular, these requirements included a .22 caliber bullet that would have ballistics of the 30-06 Springfield, retain subsonic velocity at 500 yards, and penetrate a steel helmet and a .135-inch steel plate at this distance. The cartridge should allow for a 20-round magazine capacity, rifle weight not exceeding 6 pounds, and switch from semi-auto to full-auto.

As you see, the development of a cartridge is inseparable from the development of the rifle in which it was going to be used. The result was the civilian .223 Remington cartridge intended for the AR-15 rifle introduced by the Armalite in the late 50s. Several years later, the military adopted the new combo as the M16 rifle and the 5.56 NATO cartridge.

5.56 NATO vs. 223 Rem

Though the 5.56 NATO was developed based on the .223 Remington, it doesn’t mean you can use the cartridges interchangeably. Both of them are nearly identical in terms of the external dimensions. The difference is inside the case and, surprisingly, the rifle.

The 5.56 NATO has slightly thicker walls and, thus, less case capacity, which leads to more pressure from burning the same amount of powder in a smaller space. It’s hard to compare the cartridges in terms of pressure since civilian and military testing techniques are different. But typically, the 5.56 NATO is a higher-pressure round than the .223 Remington.

Another difference lies in the rifle chamber. Everything in a 5.56 chamber is longer and thicker to withstand the higher pressures of the 5.56 cartridge. It means it’s completely safe to use .223 ammo with a 5.56 rifle, but it’s not recommended to do the other way around. A .223 chamber merely has less space for the 5.56 round to build up the pressure safely.

Though many shooters fire the 5.56 NATO from the .223 Rem rifle and don’t experience any immediate malfunctions and accidents, repeated exposure to higher pressures can lead to problems later. So you’d better stick to your rifle specifications.

5.56 Ammo Types: M855 vs M193

Before we touch on what is the best 5.56 ammo, we should run through the types of 5.56 ammo for you to choose the right load for your application. When the military created its own variant of the civilian .223 Rem, its name precisely was “Cartridge, 5.56mm ball, M193.” The M193 accepted a 55-grain projectile that was full metal jacketed and boat-tailed for improved flight performance. However, such a lightweight bullet was still insufficient for penetrating hard targets at long range.

So, in 1980, the upgraded 5.56 NATO cartridge came to the scene, the M855. The M855 had a heavier 62-grain bullet which, again, was full metal jacketed and boat-tailed but also had a steel core instead of a lead core used in the original M193. The military decided to paint steel-core bullet tips of the new M855 in green to aid in distinguishing between the two loads. That’s how green-tip rounds appeared.

Many believe green-tipped 5.56 NATO rounds are armor-penetrating, but that’s a misconception. The steel used in the M855 core is actually softer than the one typically used in armor plates. Softer steel versus harder steel? The logic suggests the latter wins.

However, the M855 is still effective against other hard objects, such as cinder blocks. On the other hand, once an M193 bullet hits a hard target, its lead core disintegrates and deforms earlier, which adversely impacts penetration.

Despite the inferior penetrating capabilities of a lead core, a higher velocity of a lighter M193 bullet makes the cartridge suitable for situations where you need a projectile that flies faster and longer. At short range, say 100 yards, it shows a pretty decent penetration. Plus, M193 bullets tend to fragment upon impact, causing tissue damage and ultimately making the 5.56 M193 round a viable option for home defense.

M855:

• Designed for penetration and long-range performance.
• Features a 62-grain green-tipped bullet with a steel core and copper jacket.
• Effective at penetrating thin metals, thick clothing, and brush cover but struggles with harder barriers (e.g., auto glass, body armor).
• Less suited for self-defense due to a tendency to pass through targets without significant tissue damage.
• Requires a faster barrel twist rate (1:7 or 1:8) for proper stabilization.

M193:

• Standard U.S. military ammunition until the 1980s.
• Features a lighter 55-grain full metal jacket round.
• Known for its ability to fragment upon impact, causing more tissue damage when unimpeded.
• Less effective at penetrating cover or barriers (e.g., metal, foliage).
• Compatible with a wider variety of barrel twist rates (e.g., 1:12), making it versatile for civilian-use firearms.

Is M193 5.56 Ball Ammo Suitable for Home Defense?

When evaluating 5.56 ammo for home defense, M193 full metal jacket rounds often come into the discussion due to their affordability and widely known performance characteristics. But is ball ammo suitable for home defense? Surprisingly, it can be.

The 5.56 NATO, being a military cartridge, means most 5.56 ammo offerings will be FMJ. Why do the military use FMJs that don’t expand and can overpenetrate? Mainly it’s because it’s cheaper and feeds more reliably. It’s also because the Hague Conventions forbids the use of projectiles that expand and flatten in the human body and cause unnecessary suffering as the warfare isn’t about killing all your enemies but rather forcing them out of action.

Now, let’s discuss the use of 5.56 ball ammo for civilian defense. First of all, do not use 5.56 M855 ammo for home defense. Featuring a steel core and a jacketed bullet, this cartridge was intended to penetrate barriers like thin metals, thick clothing, and brush cover and it doesn’t fragment, which means it poses a risk of overpenetration in practical home defense scenarios. It’s a good military cartridge, but bad for home defense.

What about the M193 5.56 for home defense? One distinct characteristic of M193 is its tendency to tumble and fragment upon hitting softer barriers, such as drywall. Fragmentation reduces the bullet’s speed and energy, posing less risk of over-penetration compared to the heavier M855 green tip rounds or 9mm FMJ handgun ammo.

That said, proper shot placement remains critical since nearly all rounds will penetrate drywall to some extent.

However, reliable fragmentation is only achievable with AR15 rifles with barrels 14.5 inches or longer because they can produce enough velocity. When a M193 5.56 bullet impacts a target with a velocity of above 2,700 fps, the bullet rapidly yaws within soft tissue, creating large wound channels. This makes it effective for neutralizing threats in typical home-defense distances, which are often within 50 yards.

On the other hand, fired from a shorter barrel (10.5″ or 11.5″ SBRs), the bullet often fails to achieve 2,700 fps, and ability to fragment becomes unreliable, resulting in shallow, narrow wound channels and potentially overpenetration.

So while M193 5.56 ammo is affordable and accessible, for home defense, it’s better to opt for purpose-built defensive loads designed for controlled expansion and reduced over-penetration. These rounds balance effectiveness and safety, making them well-suited for indoor use or areas with close-proximity neighbors.

M855 Best Applications:

• Ideal for military or defense scenarios requiring penetration.
• Effective for longer ranges and overcoming environmental challenges like wind.

M193 Best Applications:

• Perfect for training, range shooting, and short-range hunting.
• Can be used for self-defense due to its fragmentation and tissue damage potential.
• More affordable and widely available.