5.56 Vs 9mm: A Complete Review

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Whether for hunting or home defense, you want a cartridge that has the required stopping power and ballistics to match. Is a rifle or handgun chambered in 5.56 vs. 9mm Parabellum the better firearm or will there be issues such as over-penetration?  

Compared to a carbine round, pistol cartridges such as the 9mm are more common on the range. But as a shooter, you prefer a caliber of slug that has weight, placement capabilities as well as penetration. 

Technical Specifications for 5.56 vs. 9mm Rounds

One of the feelings any person might get is that 9mm is bigger than 5.56mm cartridges. This is however a misnomer in bullet nomenclature, which measures the width of the slug rather than cartridge length, dimensions. 

The 9mm Parabellum weighs 124 grains avoirdupois, starting at speed of 1,200 feet per second. This makes it similar in ballistics to a heavy .357 magnum load, and for a handgun round, this is hot.

The actual muzzle departure velocity for 9mm rounds is approximately 4000-foot pounds, which technically suits handgun usage.

Bullets for the 5.56 NATO cartridges weigh 62 grains and will leave the muzzle at speeds of 3,200 fps. 

As the main standard NATO rounds, the 5.56 vs. 9mm are also measured by length as well as caliber (width). The cartridges have the designations 5.56x45mm and 9x19mm, meaning there’s a lot more room for powder in the rifle round. 

This is where the bullet gets the bang; gaining more out of the barrel (muzzle) speed of about 1,300 ft. lbs. Knock-down kinetic energy is the punch that you want to be transferred to your target.

The 9mm bullet weighs 7.45 grams with a velocity of 407 meters per second which translates to 455-foot pounds or 617 joules. 5.56mm on the other hand weighs 4 grams and at a velocity of 864 m/s will deliver 1,328-foot pounds or 1,801 joules.

Speed and Energy of the 5.56 vs. 9mm Bullet 

In terms of energy, the 5.56 round will deliver three times the energy of a 9mm revolver bullet.

If I am looking at the damage, significant punishment is taken by ballistic gel trying to stop the 9mm round. This is however in comparison to other handgun rounds, as rifle bullets will cause considerable damage with secondary projectiles.

When a 5.56 bullet travels at full speed, it’s prone to fragmentation and the aforementioned tumbling. This causes more damage to soft tissue and bone than the 9mm whose speed threshold is considered to be 1,600 fps. 

Currently, some rounds are faster and stable than earlier NATO versions. At close range, the 5.56 vs. 9mm slugs will be able to devastatingly wound your target.

Overall accuracy, however, and long-range terminal ballistics will need to be sacrificed for the terminal stopping power of the 9mm bullet.

Rifle rounds on the other hand have more kill (kinetic) power. This is possible even at long ranges if you have the proper shot placement. 

Reasons attributed to the more deadly energy for 5.56x45mm NATO cartridge include;

Gas Pressure

A 5.56 mm rifle round has higher pressure gas which results from the imploding and expanding powder.  This pushes the slug out at a higher rate than a 9mm bullet. 

The 5.56x45mm NATO cartridge offers about 55,000 PSI versus the 9mm’s 35,000 PSI of internal gas pressure. 


It only makes sense that the larger cartridge has an equally significant amount of powder to burn. The 5.56 round’s case volume holds approximately 56 grains of smokeless powder as opposed to the 4 grains of a 9mm Luger cartridge. 

Barrel Lengths

As the cartridge releases the slug, the gas pressure will push it past the length of the barrel. Unless you are looking at the 9mm as a carbine round, rifle barrels trump in length dimensions to handguns. 

I could compare the length of s typical rifle that fires 5.56 caliber at between 15 and 26 inches. This is incomparable to a pistol or revolvers three to six-inch barrel lengths.  

Mass of the Bullet

When investigating muzzle energy, you must consider bullet mass as well. A lighter bullet will leave the barrel with more speed but a heavier one will have more energy. 

Squaring off the slug’s speed will give you the kinetic energy. Given that practicality, a lighter bullet will travel faster, picking up more velocity to deliver greater muzzle energy.

If I were to talk sorely on stopping power, the effective range and energy of rifle bullets over handguns is immeasurable. The 9mm slug gets the most from a shorter barrel due to its design, but the final impact will be determined by what it is and how far the target is. 

The longer barrel required when shooting 5.56mm rounds make a difference, but suppose you fired the slug from a pistol? A 9mm round won’t benefit much from barrels longer than 9 inches, while the rifle bullet is still being pushed by gas at 16 inches. 

Leveraging the Tumbling 5.56 vs. 9mm Penetration

All stopping power rounds will have an over-penetration, making them effective against game or lethal threat. 

Recently, I participated in a class for training law enforcement officers. Incidentally, there was an accidental discharge in the class due to negligence by one of the trainees.

This round was a 9mm 124-grain hollow-point slug, one of the best penetrators. An investigation later found that the bullet had expanded as it plugged through 6 panels of drywall before it stopped. 

A 5.56x45mm round will penetrate a few layers of the drywall as well, but it’s designed to tumble. This makes it to become unstable and disintegrate into pieces, causing penetration to become limited.

During the Black Hawk Down scenario in Africa, Somali fighters earned the nickname ‘skinnies’. This was because shooters couldn’t put the tumbling 5.56 round through the slender sized guerillas with any effect. 

The standard M855 round used by US marines is designed to create a devastating wound with its tumble. But to do so it needs to travel into the body far enough, and for many Somalis, there just wasn’t that much body. 

The resultant wound would resemble something that was caused by an icepick that had a bullet. 5.56 NATO rounds would zip through the fighter’s, no pun intended, skinny bodies.

There would be no devastating wound despite the larger caliber of 5.56 vs. 9mm handgun rounds that create a massive internal cavity. The tumbling round also expends the muzzle energy and velocity sooner, traveling an unpredictable path and at a shorter distance.

Talk of Speed

The speed of a projectile and the distance to target must also be factored into the tumbling equation. A firearms instructor once narrated to me how a guy stumbled while walking in a single file, shooting the person in front at the hip.

The round was a .223 Remington, very similar to the 5.56x45mm. Its tumble created a 90° trajectory from the victim’s hip to his heart, killing him on the spot. 

Shot placement for 5.56 vs. 9mm Rounds

You shouldn’t be concerned about how much energy or penetration you’ll get from a 5.56 vs. 9mm round if you’ll miss the target. As a shooting instructor, I tell my trainees to place as few hits as possible to stop the threat or game.

I don’t doubt that the 5.56 caliber is stronger than the 9mm pistol round at stopping targets. But does either of these rounds increase your odds at hitting targets solidly?

Accuracy is made easier by longer barreled and shoulder-mounted rifles as opposed to handguns. But for both rounds, shot placement will depend on how much you are practicing as an on-target shooter.

If you are involved in a gunfight, such as an ambush situation, you are looking to place more shots on your target without missing. Shooting the ground or bushes around an attacker only alerts them to your position, giving them time to accurately return fire. 

It’s, therefore, easier to place shots accurately with a rifle than a handgun, but what about the rounds?

Testing the 5.56 vs. 9mm in Similar Sized Guns

For such a review, I’ve secured a pair of M4 carbines capable of handling the 5.56x45mm NATO and 9x19mm Parabellum rounds.  Both carbines have 16-inch barrels with one chambering in 9mm and the other 5.56mm or .223 Remington.

These carbines feature 4-way aluminum forearms for the rail, retractable stock, and flat-top receivers.

For the 5.56mm carbine, its barrel has rifling in one-in-seven right-hand twist. Its 9mm counterpart uses one in ten rifling.

I equipped both barrels with birdcage flash suppressors, NATO-style, plus a Picatinny gas block. The 9mm carbine had a recoil-operated straight blowback action while its partner used a gas-piston mechanism.

Standard AR configurations were set for the external controls of both my test carbines. These include the trigger, magazine release, bolt catch, and manual safety lever.

The only variance was in the 5.56 model, which used a lower receiver in standard AR configuration fed by a similarly styled magazine. A dedicated lower receiver featured on the 9mm carbine, not modified or plugged AR model. 

The 9mm caliber carbine was fed by a 32 round metal-form stick magazine. 

With both my firearms installed with a dual circle and dot sights, I zeroed my carbines for 50 yards.

5.56x45mm NATO

While a powerful round, the 5.56 has the power to immediately incapacitate or stop your target. With suppression, I can make the carbine muzzle power for this round similar to that of the larger 7.62mm NATO.

Close quarter shots with 5.56 proved effective, especially against light obstacles. I have always found this cartridge to perform better when training shooters that come with minimal rifle exposure. 

The overall shooting experience with my lightweight assault carbine is undeniably excellent.  Having zeroed my optics property, I placed some downrange test patterns with predictably tight grouping at 50 yards. 

My 1.17-inch cluster for three shots at this range proved that the 5.56 ammo and the carbine combination can be relied on.

9x19mm Parabellum 

This is the most used cartridge for handguns and submachine guns by much of the world’s military. It’s claimed that around 60% of law enforcement firearms are chambered in 9mm Parabellum.

The 9mm round is also responsible for making pistol handguns more popular than their revolver counterparts.  A low cost round, its availability, and belief for effectiveness has led to its self-defense and police applications. 

I tested the Winchester PDX1 for the 9mm caliber carbine, ammunition marketed specifically for personal protection.  These rounds had a 147-grain weight, a copper shaded slug that’s at the heart of the Ranger LE ammo line by Winchester.

From my 16 inch barrel, I measured an average of 1,140 fps using a chronograph. Several groups on paper at 50 yards confirmed my best cluster at 1.25 inches. 

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The Final Verdict on 5.56 vs. 9mm Ammunition

While my review is about ammo and guns, it comes down to more than that. I constructed real obstacles and barriers to testing performance for the cartridge’s real-world application.

My initial conversation confirmed that the 5.56 mm slug wasn’t likely to penetrate further than its 9mm rival.

When it came to accuracy, both rounds stood their ground within respective parameters to prove they were suitable for personal or household defense options. Performance-wise, a rifle or carbine is easier to aim, control, and has a defined impact transfer of energy.

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