The Best 5.56 Round for Home Defense and CQB: Diving into the Research

I bet many of you could probably give me your choice for the best 5.56mm round for home defense or CQB. The problem is, that you’re most likely wrong. You would be hard pressed to name an area of study that is plagued by more misinformation than ballistics and ammunition testing. In this article we will review some incredible research, that will show you why looking at ballistics gel tests, and foot pounds of energy are not nearly enough to select an appropriate round.

I’m not going to beat around the bush here. There is no magical 5.56 round that will outperform any other round in all situations. You must understand that shot placement will always trump the minutia of ballistics. The kind of performance differences we will be discussing in this article amount to a few percentage points of difference at best.

We also must remember that ammunition is situation specific. Some types of ammo are designed to work well, penetrating through intermediate barriers such as glass or metal. Other types of ammunition are designed to do the exact opposite, by not penetrating easily through such barriers.

In our quest to understand how to select our round we need to discuss the basics of ballistics.

Ballistics

Most folks are not as nerdy as I am. This is a fact, just ask my wife. When they mention ballistics they are generally referring to a bullet in flight. That is not wrong, but there are actually three types of ballistics: internal, external and terminal ballistics. Most folks make the mistake of studying only one of these which leads them down the wrong path for round selection.

Internal Ballistics

Internal ballistics is the study of a round from the time the primer is struck by the firing pin, until the round leaves the barrel. This is incredibly important as things like chamber pressures must be understood or you might blow your gun up. This area of study is of great interest to ammunition and firearm manufacturers, but of less utility for us.

External Ballistics

External ballistics is the study of bullets in flight, prior to striking their targets. This is one area where almost everyone has been fooled by Hollywood. For example, I bet you think bullets fly in a perfect spiral, once they leave the barrel. As you might guess this is categorically incorrect.

The rifling in the the barrel does spin the bullet as it leaves, but as a matter of fact, the bullet does not move in a perfect spiral. The bullet will yaw around its axis, in the first 50-100m for 5.56 rounds. Eventually it ends up in a near perfect spiral through the mid range of it’s trajectory. As it loses velocity it becomes unstable and will yaw, and tumble until it hits the ground. This is assuming it doesn’t striking anything in between.

As you will see bullet yaw is incredibly important for selecting an appropriate self defense and CQB bullet for 5.56. It is also one reason why ballistics gel, and energy tests are not the complete story for selecting a round.

Terminal Ballistics

Terminal ballistics is the study of bullets and their effects on a target. For the purposes of this article, that target is a human. Human targets make it very hard to predict, with any certainty, what effect any given bullet will have.

As you might imagine shooting a 140 pound person can be much different than a 240 person. There are also many different structures in the body that can cause a bullet to deflect or break apart, or pass through with comparatively little damage.

The ideal 5.56 bullet would penetrate just far enough to reach vital organs and expend all it’s energy without exiting. This round does not exist, and not likely to be a reality any time soon.

Now that we have a decent understanding of the factors that are in play when talking about a round, let’s look at some detailed research to see what factors matter in selecting a 5.56 round for home defense or cqb.

Terminal Performance in Bullets

As we’ve alluded, there are numerous factors that affect the lethality of a bullet. Commonly you will hear folks talk about bullet velocity and subsequently the energy the bullet has when it strikes a target in foot pounds (ft-lbs)

A bullet’s energy is a relevant factor to discuss, but it doesn’t tell the whole story. Imagine a shotgun round filled with small bird shot. Objectively it has a lot of energy but the mass of each small pellet is such that it generally won’t penetrate past skin and muscle on a human. This makes it a bad defensive round, regardless of the amount of energy in the shell.

More advanced readers might be familiar with ballistics gel testing. These tests are commonly performed by the military and numerous police agencies. These bullets are fired at a block of gelatin that is made of a known mass and density. Researchers then look for the amount of expansion, retained weight, and penetration of the round.

These blocks of gelatin mimic the average density of the human body, and can be used as a proxy for penetration in a human. As we stated above, this is not the whole story. Humans have bones, tendons, and other structures that can deflect rounds, where as gelatin does not. This is not the only problem, as you will see.

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Bullet Yaw in Ballistics Gelatin

In 2008 the Army was receiving reports from soldiers that their 5.56 rounds were commonly passing through enemy combatants, without killing them. The Army took it upon themselves to examine the lethality of their 5.56 rounds and compare it to the best commercially available rounds of various types and weights in 5.56mm.

They found when they were comparing data, amongst other agencies that do ballistics gel testing, that radically different results would be obtained with identical batches of bullets. This stumped them for a little while.

Eventually they began to examine the bullet in flight, not just it’s effects in the gelatin. They discovered that bullets were often entering the gel with different yaw angles. Check this photo out to see what I mean.

In the top photo, you can see the bullet enters the ballistics gel with almost no yaw angle. This produced deep penetration with almost no damage the bullet.

In the bottom photo you can see the bullet enters the gelatin at a high yaw angle. This caused the bullet to immediately destabilize and break apart. These are the exact same rounds, and the exact same gelatin, with completely different results.

Some of you might be thinking that all we need is super high yaw ammo and we will be set. Well you might be correct if you only had to contend with human tissue. However, if you have to shoot through walls, glass, or metal a high yaw bullet will not penetrate effectively.

Which Rounds Did the Army Determine Were More Lethal?

After testing numerous rounds, everything from 40 grain bullets all the way up to 100g 5.56 rounds (didn’t know that was a thing), they found that there were no clearly superior rounds to the venerable 62 grain green tip round. Check out this chart from the study.

This chart compares the lethality of all commercially available rounds (in 2008) against several issued 5.56mm rounds and they found no profound differences.

This chart shows lethality relative to distance. Higher on the chart means the round is more lethal. You can clearly see that some rounds are a little higher than others, and in general, the lethality decreases as distance increases.

They even compared these 5.56 rounds against a heavier, more powerful 7.62 round which actually performed the poorest. Remember that energy and penetration in gelatin doesn’t mean the round “has more stopping power.”

Increasing a 5.56 Bullet’s Lethality

This leaves us in a bit of a conundrum. Some rounds will over penetrate when they strike humans, as a result of their yaw. In fact that is much more likely to occur within the first 50 meters of the bullet’s flight. Check out these graphics.

These graphics show that the M855 round (62 grain green tip) yaws quite a lot in the first 50 meters. It eventually looses almost all of it’s yaw around the 200m mark and continues in a near perfect spiral.

Upon further analysis, the Army realized the only way to increase the odds of shoot an enemy with a favorable yaw rate was to shoot them more. This effectively increases the odds of a bullet that will destabilize quickly.

Using the same lethality measurement tool you can see that a pair of shots show more consistency. It also demonstrates much higher lethality compared to single shots. This is no great surprise, but this does show that longer strings of fire are needed in training.

5.56 Rounds Through Glass, Metal and More

Needless to say, this is not the end of the discussion. Often times we are forced to consider a round’s effects through barriers both before and after the target.

If we are looking to defend our home, we should not select a round that will blow through 10 walls. Similarly, if we are a tactical unit that does vehicle interdictions regularly, we should only consider rounds that perform well through glass and metal.

This article from Active Response Training, is very detailed. In it they conduct numerous ballistics gel tests through glass and metal. They also place layers of cloth in front of the gel to mimic clothing. I wish they had captured yaw data, but no one’s perfect.

Bullet Testing Results

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Shooting Through Glass Barriers: Hornady 55 grain GMX

Rounds with Least Penetration Through Barrier: Hornady Tap Urban

General Purpose Ammo: Federal Tactical 62 grain LE

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All of these are solid performers, however, we need to remember that when the army tested numerous different rounds they found very little practical difference. Now I think there have been some developments since 2008 and there are some recommendations that we can safely make.

First, if you are defending your home, I would recommend the Hornady Tap Urban. It has good penetration and will break apart upon hitting barriers, thus mitigating over penetration issues

You can see that when this round hits bare gelatin it penetrates around 9 inches. This is perfect for most sizes of humans. However, when you look at it’s performance through barriers the round becomes completely pulverized, with only particulate penetration. It goes without saying that this round is a no go through barriers of any type.

The Hornady GMX round does very well through barriers. This might be a good round for tactical units that might have to shoot through intermediate barriers.

You can see that regardless of the intermediate barrier the penetration is about the same, as are the other characteristics. This would work well in a wide variety of situations.

Final Thoughts

We’ve covered a lot in this article, and we’ve seen that ballistic gel, and foot pounds of energy are certainly viable metrics, but they aren’t the full picture.

In order to best evaluate the round you need to pay attention to the projectiles external ballistics as well as it’s terminal ballistic profile. Crucially, we should seek out different types of yaw data for a more complete picture of any given round’s efficacy.

Lastly, remember what I said in the beginning of the article. These differences while measurable, are not going to turn your AR15 into an unstoppable killing machine. You need solid skills, and the ability to place more than one round on target. Now get out there, and get training!