The 5.56 vs 7.62 rifle caliber debate is a never ending internet argument, filled with anecdotes, and superfluous nonsense. In this article we will examine these common calibers from a scientific perspective to determine which is the best. Needless to say, theres a lot more to consider than stopping power or bullet speed. Let’s get to the details.
The first thing we need to note is that this comparison is between the standard NATO 5.56 x 45 and 7.62 x 51mm calibers. We aren’t going to discuss the 7.62 x 39, most commonly used in AK-47 style rifles. There’s nothing wrong with that round, it’s just beyond the scope of this article.
Long time readers of this website will know that I’ve written about rifle caliber and pistol caliber comparisons previously. The long and short of it is that shot placement trumps any caliber considerations, at least in calibers that are man portable. Check out the 5.56 vs 7.62 overview below.
5.56×45 vs 7.62x51mm Caliber Comparison
- Data derived from NATO comparisons
- Theoretical data confirmed with biological tissue testing
- 7.62 and 5.56 similar exterior ballistics
- 7.62 rounds carry roughly double the kinetic energy
- 5.56 rounds don’t require long barrels for high velocity
- 5.56 M855 rounds penetrate thin metal better than 7.62 at longer ranges
- 5.56 Easier to shoot with less recoil
Just to avoid miscommunications, I will be referring to these calibers as .223 for 5.56 and .308 for the 7.62 mm cartridge. They aren’t technically the same but the terms are interchanged commonly. If you like this kind of in depth article, then you should join the email list below.
Now that we have some of the preliminary info out of the way, let’s quickly review the basics of terminal ballistics. This will make some of the concepts easier to understand later on.
Terminal Wounding Ballistics
Any bullet works in only two ways. The first mechanism of wounding is the crushing injury of the bullet pushing through soft tissue. It’s limited to the width of the bullet, and is generally the only way that pistol calibers function.
Rifle rounds use this first mechanism as well as more injurious second method. Because a lighter rifle bullet travels much faster than a pistol round, they create a temporary wound cavity, as they enter tissue. This cavity is many times the width of the bullet, and causes much more tissue disruption. This is the primary reason why rifle bullets are more lethal than pistol rounds. They’re just different cartridges using different wounding mechanisms.
If you read my article on rifle and pistol stopping power which examined over 1800 shootings, you know that getting shot, even with large caliber rounds isn’t always a one shot stop. In fact, you’ll rarely see this regardless of the intermediate cartridge you use. This leads us to the practical way that wounding affects people.
Psychological and Physiological Wounding
Broadly speaking there are two ways to stop someone by shooting them with a firearm. The first method is a central nervous system hit. This physically incapacitates a person by preventing the brains electrical signals from controlling the functions of the body. I’ll call this a physiological stop, as the person cannot physically continue to fight.
The second method is a psychological stop. This occurs when a person is shot, and stops fighting, or retreats due to the threat of further injury or death. This is the most common method, as any other hit on the body, apart from a central nervous system hit, falls into this category.
People in this group are stopping due to the pain and psychological fear of further injury or death. Many shot people live, and if they die, it will take minutes to hours before they lose enough blood to be fatal.
Now that we’ve reviewed the basics of terminal wounding, let’s take a look how the 7.62 and 5.56 mm round perform.
5.56 vs 7.62 Caliber Comparison
Most shooters who compare these two calibers often fall into the easy thinking that because the 7.62 round is bigger, and more powerful, then it must be a better round for self defense, law enforcement, or military applications. This is also true for the close range long range debate. As you’ll see, this isn’t really true, but not for the reasons you think.
In this section we’ll review the practical, and quantifiable differences in these rounds. Later on we’ll cover the practicalities of shooting, and carrying rifles that are chambered in these calibers. Now let’s talk about muzzle energy for each round.
5.56 vs 7.62 Kinetic Energy Comparison
There is no doubt that the 7.62 mm NATO cartridge carries more energy than the 5.56 round. This is indisputable. The 7.62 has a larger bullet diameter and almost triple the bullet weight. Even when comparing the 5.56 round out of a 20 inch barrel, the 7.62 has much more energy. Check out this chart below.
This chart comes from a NATO briefing on the lethality of the 5.56 round. You can check it out here, if you want to see more info. I know these numbers are using the nasty metric system, but I’ll translate. The 5.56 NATO round has 1254 ft/lbs of energy. The 7.62 NATO round has 2434 ft/lbs of enrergy. The 50 caliber round has a whopping is 12,538 ft/lbs. That heavier bullet is really moving!
This chart shows that all soldiers need to be carrying 50 caliber rifles! Just kidding, that’s not practical, for many of the same reasons 7.62 isn’t practical. Next let’s look at the trajectories of the 5.56 vs 7.62 rounds
5.56 vs 7.62 Bullet Trajectory
The trajectory of these rounds is surprisingly close. In the chart below we can see that a 308 rifle with a 20 inch barrel is almost identical to your standard United States M4 carbine, with a 14.5 inch barrel.
Contrary to popular belief, the 5.56 round performs very well out of short barreled rifles. This is because the 5.56 round achieves high muzzle velocity, even from a relatively short barrel length .
In the chart below you’ll see that the 223 round is still going over 2300 feet per second, from an 8.3 inch barrel. With a longer 16-20 inch barrel it has a much flatter trajectory, compared to the 7.62. They both have a similar effective range.
These two figures indicate that the 5.56 round is roughly as fast as any 7.62 round, even when fired out of a very compact rifle. The obvious trade off is the amount of energy that the 7.62 rifle generates out of that longer barrel. When you compare the energy dump, between the two calibers, you see that it may not be as drastic as you think.
These values correspond to 134 ft / lbs for the 5.56 NATO and 184 ft / lbs for the 7.62 NATO. These figures show that at longer distances these rounds are different. However this doesn’t mean that the larger round is actually stopping someone any faster. After all, if a pedestrian is hit by a Honda Civic or a dump truck, they’re both effectively stopped!
I’ve showed you a lot of charts and data from tests, but it’s important to take a look at these rounds performance in a more realistic manner. In the next section you’ll see how these rounds really performed in biological tissue. Hopefully this can help you make an informed decision.
5.56 vs 7.62 In Biological Tissue
Tests with calibrated blocks of gel, or ballistic soap are fine, but those are only approximations of their performance in human tissue. The authors in this study actually shot sheep that had been euthanized, in order to determine the actual effects of different NATO rounds on an extremity wound. Check the infographic out below.
Its pretty clear from the X-rays that the M80 ball rounds caused more damage, due to higher energy affecting the tissue. Furthermore, it also caused a larger exit wound, compared to the 5.56 round. That settles it right, 7.62 takes the cake! Not so fast.
On paper the 7.62 round does deliver better performance. However, there are some practical considerations that really matter, for those that are actually carrying a rifle for home defense, or tactical applications. In the next section we’ll cover the realities of making this decision, for your specific needs.
Choosing Between 7.62 and 5.56mm
My goal for this section is to highlight some practical considerations for those trying to determine which caliber they should choose. The first and most obvious consideration is the increased weight of a 7.62 x 51 NATO weapon system and ammo.
To illustrate this point, we’ll compare the overall weight increase of a solider issued a 7.62 x 51 rifle. To make this comparison cool, we’ll use the badass HK MR762 rifle in the SDMR format from the US Army and other military forces. Heckler and Koch states this rifle weighs 9.84 pounds without a magazine.
A fully loaded HK magazine is 1.62 pounds with all 20 rounds. I know the picture shows a 10 round mag but I doubt that’s all the soldiers will be using. The standard US Army optic from Sig weighs 1.12 pounds. The bipod weighs .875 pounds. The suppressor weighs .74 pounds. The flashlight weighs .34 pounds, and the NGAL laser weighs .25 pounds. This totals 14.8 pounds.
A standard M4 5.56 rifle weighs 6.6 pounds. The standard issue ACOG is .93 pounds. A fully loaded PMAG is 1.11 pounds. If we assume they have the same light and laser system, and a plastic vertical fore grip, this brings the total unit weight to 9.5 pounds.
If we consider that a standard combat load is 210 rounds. This brings the total 7.62 system weight to 30.3 pounds. The standard 5.56 total system weight is 16.2 pounds.
Keep in mind the SDMR rifle is much lighter than most sniper rifles and medium machine guns. This drastic weight increase will cause friendly casualties. Let me explain.
Weight = Casualties
If you read my previous article on ultra light weight tactical gear, you’ll remember I highlighted some interesting research. In that article research highlights that on average, if you add 15 pounds of weight to every person in a Marine Corps rifle squad, in an attack, it will produce 1 more casualty for every simulation. This is true even if you add this weight in the form of better body armor.
We can see that we’ve added nearly 15 pounds with a heavier weapon system. Sure, we’ve got a more energetic round, but the extra cost of carrying this weight around is a huge liability for infantry forces. In my opinion any weapon system that drastically increases the average infantryman’s weight is not worth it. Otherwise they should all carry 50 caliber rifles!
I know I can hear some of you now, “what about long distance performance?” Well let’s look at that. Take a gander at the chart below. This data comes from a military analysis of over 133 gunfights from World War 2 to the Global War on Terror.
The researchers determined, from one on one interviews, the most common requirements of combat marksmanship. Surprise, surprise, short rapid engagement, in uncertain lighting conditions, is the most common close combat shooting requirement.
I don’t think anyone will claim they could shoot a 7.62 rifle faster or more accurately than they could a 5.56 rifle. This certainly isn’t true for the average solider or Marine. A Low recoil, compact assault rifles is certainly more controllable than large caliber semi-automatic rifles. This leaves us with the question. Who is the 7.62 rifle good for?
Who is 7.62 Best For?
In my opinion 7.62 caliber rifles are best for those that don’t have to carry the weight over long distances, or sprint with the rifle. If you’re primarily deploying from a vehicle, then 7.62 might be a good choice. Similarly, if you need improved terminal performance, then 7.62 would be a better option, especially for long-range shooting.
If there’s a chance that you will have to engage in close combat, where targets are fleeting, and will require multiple shot engagements, then 7.62 mm is not good choice.
I think it makes sense for small units like infantry squads and rural SWAT teams to have a 7.62 (or similar) capability, with one or two members, provided it makes sense for the operational environment. Moving a DMR gun while clearing an apartment at close quarters doesn’t sound fun to me!
Further more, it would be a good idea to assign the 7.62 rifle to a bigger team member. Research consistently shows that total load shouldn’t exceed 30% of the persons weight. If your team is issuing all the Gucci gear in my ultralight weight gear review. That means the realistic floor for a full combat load out for a soldier is 215 pounds, in good shape.
You’ll note that this is for an infantryman carrying a 7.62 rifle. A SWAT officer wouldn’t carry more than 2-3 magazines for a DMR gun, bringing the size requirement to something like 195 lbs. Now let’s wrap this 5.56 vs 7.62 article up.
Final Thoughts
I don’t want you to think that I’m crapping on 7.62 guns. It’s a great cartridge. They certainly have practical applications, but they aren’t some super caliber that will magically drop bad guys. If you talk with any whitetail deer hunter, they’ll tell you that game shot with a 308 takes time to die. Unless you happen to hit the central nervous system.
If you really need longer range capability you’re probably a little better off looking at 6.5 Creedmoor, especially in bolt action rifles. It’s a bit faster, with similar terminal effects. Otherwise you’d be better off with a quality 5.56 mm rifle for most short, to intermediate range tasks. There’s a reason why the U. S. Military, and most NATO forces still prefer 5.56 for the assault rifle.
If you have any comments or questions, put them in the comments section below, and I’ll get you an answer. Don’t forget to join the email list below. Now get out there and get training.
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