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5.56 NATO Vs. 6.5 Grendel: The Future Is Now


When it comes to rifle cartridges, there are numerous options available, each designed to excel in specific scenarios. Two popular choices among firearm enthusiasts are 6.5 Grendel and 5.56 NATO. 

In this guide, we’ll explore the history, dimensions, ballistic performance, real-world uses, and more of these two excellent cartridges. By the time we’re through, you should have a clear understanding of their similarities and differences, as well as which one should suit you better.

So let’s get to it. 

Some Important Background

Let’s kick things off with a quick history lesson. 5.56 NATO has a longer history, so let’s start there.

5.56 NATO got its start back in the 1960s when it was adopted by the United States military as the standard round for the M16 rifle. The goal was to create a smaller, lighter, and faster round that would provide soldiers with increased ammunition capacity and controllability in combat situations.

Its small size and high velocity allowed soldiers to carry more ammunition while still maintaining sufficient lethality. The 5.56 NATO quickly gained popularity and became one of the most widely used rifle cartridges worldwide.

6.5 Grendel, on the other hand, is a more recent development. It was designed by Bill Alexander of Alexander Arms in the early 2000s. The goal was to create a cartridge that offered superior long-range accuracy and energy retention compared to 5.56 NATO, without sacrificing magazine capacity or requiring extensive modifications to the AR-15 platform.

Alexander Arms 6.5 Grendel Integrally Suppressed

Alexander achieved this goal by using a larger case with a wider base and a greater bullet diameter. His design focused on optimizing long-range ballistics, allowing shooters to engage targets effectively at extended distances. While 5.56 NATO was developed primarily for military applications, the 6.5 Grendel was designed with a specific emphasis on precision shooting and hunting.


While 5.56 NATO remains the go-to choice for military applications around the world, 6.5 Grendel has gained its own level of popularity among civilian shooters, hunters, and precision rifle enthusiasts.

5.56 NATO’s lightweight nature, high velocity, and effective terminal performance make it ideal for combat scenarios. It offers excellent penetration and fragmentation, ensuring the ability to incapacitate targets while minimizing the risk of over-penetration. 

Plus, the widespread availability of 5.56 NATO ammunition and the vast range of rifles chambered in this caliber make it a convenient choice for military and law enforcement agencies.

On the other hand, the 6.5 Grendel has carved out a niche in precision shooting and hunting. The cartridge's larger bullet diameter, higher muzzle energy, and exceptional long-range ballistics make it well-suited for engaging targets at extended distances. 

Precision shooters appreciate the 6.5 Grendel for its inherent accuracy, flat trajectory, and superb energy retention, allowing them to consistently hit targets with precision at long ranges. 

Hunters, particularly those pursuing medium-sized game, value the 6.5 Grendel's ability to deliver significant energy and terminal performance at ranges where the 5.56 NATO may fall short.

In recent years, the popularity of the 6.5 Grendel has led to an increasing number of rifles being chambered in this caliber. Many firearm manufacturers now offer rifles specifically designed for the 6.5 Grendel, catering to the growing demand in the market.

This availability, combined with the availability of purpose-built ammunition, has made the 6.5 Grendel a viable option for shooters seeking long-range precision or hunting capabilities.


6.5 Grendel5.56 NATO
Parent Case.220 Russian.223 Remington
Bullet Diameter.264” (6.71mm).224” (5.7mm)
Neck Diameter.293” (7.44mm).253” (6.43mm)
Base Diameter.439” (11.15mm).377” (9.58mm)
Case Length1.52” (38.7mm)1.76” (44.7mm)
Overall Length2.26” (57.5mm)2.26” (57.4mm)
Case Capacity35gr H2O (2.3cm3)28.5gr H2O (1.85cm3)
Max Pressure52,000 psi62,366 psi

As you can see, 6.5 Grendel has a larger case capacity, a wider base, and a greater bullet diameter than 5.56 NATO. The larger bullet of 6.5 Grendel contributes to its improved ballistic performance, especially at longer distances, despite the lower maximum pressure.


6.5 Grendel, 123gr5.56 NATO, 55gr
Muzzle2580 FPS1818 ft-lbs-1.5”3240 FPS1282 ft-lbs-1.5”
100 Yards2374 FPS1540 ft-lbs0”2837 FPS983 ft-lbs1.4”
200 Yards2178 FPS1296 ft-lbs-4.7”2468 FPS744 ft-lbs0”
300 Yards1991 FPS1083 ft-lbs-16.7”2128 FPS553 ft-lbs-7.2”
400 Yards1815 FPS900 ft-lbs-37.6”1817 FPS403 ft-lbs-22.1”
500 Yards1650 FPS743 ft-lbs-69”1540 FPS290 ft-lbs-47.7”

*Data is the manufacturer’s advertised ballistics for Hornady Frontier FMJ

6.5 Grendel generally outperforms 5.56 NATO. 6.5 Grendel delivers higher muzzle energy and retains energy better at extended ranges. It offers increased accuracy and stopping power, making it a compelling choice for precision shooting and hunting applications.


Both 6.5 Grendel and 5.56 NATO come in a huge range of rifles. From AK patterns to bolt actions to even a few lever actions, you’d be surprised at how widespread both cartridges have become.

But the biggest and arguably best platform for both is the AR-15. Since both were designed for the AR-15, it makes sense that most people choose it.

A standard AR-15 can be chambered in 6.5 Grendel or 5.56 NATO with only 3 changes: Bolt, barrel, and magazines. And yes, I really mean just the bolt. The carrier is interchangeable, so you only need a new bolt. 

The bolt and barrel are wildly different sizes. But the magazine is a little different. 5.56 NATO mags don’t work well with 6.5 Grendel, but in a pinch, they can work, but you take a major hit to capacity and reliability. Basically, if you go to the range and only bring your 5.56 mags, you should be fine for the day. Beyond that, get mags built for 6.5 Grendel.

25-round 6.5 Grendel magazines (like this one from ASC) are the same size as 30-round 5.56 NATO mags.

All other parts are interchangeable between the two platforms. You might want a heavier buffer in the 6.5 Grendel if you use normal or light springs/weights in your AR. But if you normally run something like an H2, you’re fine.


Now let’s talk about what those numbers mean in real life.


For hunting purposes, 6.5 Grendel is often preferred due to its superior energy retention. It provides excellent accuracy, sufficient power, and the ability to take down medium-sized game at extended distances. 

Lehigh Defense Controlled Chaos Bullets 6.5 Grendel

5.56 NATO, although suitable for smaller game, is generally less ideal for hunting larger animals. You should also check local laws before using .223/5.56 for hunting since it is too small in several states.

Target Shooting

When it comes to target shooting, both cartridges can be effective, but 6.5 Grendel's ballistic performance shines through. It's superior accuracy and energy retention make it highly desirable for long-range target shooting. 

While 5.56 NATO does have a flatter trajectory at closer ranges, 6.5 Grendel is able to maintain its trajectory better past a few hundred yards. However, 5.56 NATO's lower cost and greater availability of ammunition can also make it a more practical choice for casual target shooters.


When considering self-defense applications, 5.56 NATO has long been the standard choice due to its widespread military and law enforcement use. It offers balanced penetration and terminal performance, making it effective in close-quarters engagements. 

ar 15 magazine face off
Each has their purpose, and each has their place.

6.5 Grendel, although capable of delivering more energy, is often less ideal for self-defense due to its potential for over-penetration and limited availability of defensive ammunition options.

Available Rifles and Ammo

5.56 NATO has a significant advantage here. It’s compatible with a wide range of rifles, including the popular AR-15 platform, and enjoys widespread availability of ammunition from various manufacturers. 

6.5 Grendel, while gaining popularity, has a more limited selection of rifles and ammunition options.

As mentioned above, 5.56 NATO tends to be a good bit cheaper, too, with ammo often running about half the price of an equivalent box of 6.5 Grendel.


6.5 Grendel and 5.56 NATO are both capable cartridges, each with its own strengths and areas of expertise. 6.5 Grendel offers superior long-range performance, making it a great choice for precision shooting and hunting at extended distances. 

On the other hand, 5.56 NATO is widely recognized for its effectiveness in military and self-defense applications, with abundant rifle and ammunition options available.

Ultimately, the choice between 6.5 Grendel and 5.56 NATO depends on your specific needs and preferences. If you prioritize long-range accuracy, energy retention, and hunting capabilities, 6.5 Grendel may be the better choice for you. Conversely, if you value versatility, affordability, and widespread availability, 5.56 NATO is a solid option.

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3 responses to “5.56 NATO Vs. 6.5 Grendel: The Future Is Now”

  1. Billy says:

    …then the 6mm ARC came along…

  2. Al Liguori says:

    Bill Alexander had an out-sized role in popularizing the 6.5 Grendel, but competitive shooter Arne Brennan (of Houston, Texas) and Lapua ballistician Janne Pohjoispää, deserve recognition for their pivotal roles.

    If you had zeroed the 5.56 Nato at 100yds as you did the 6.5 Grendel, the 5.56 NATO would have shown even poorer performance.

  3. Harold Littell says:

    Where the 6.5 Grendel hidden gem shines is for PSD. Compare it to the 5.56 out of 12″ barrels. The 6.5 is better at 300m than the 5.56 at 100m. I’d love to see it become more popular.

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  • Bill Alexander had an out-sized role in popularizing the 6.5 Grendel, but competitive shooter Arne Brennan (of Houston, Texas) and Lapua ballistician Janne Pohjoispää, deserve recognition for their pivotal roles.

    If you had zeroed the 5.56 Nato at 100yds as you did the 6.5 Grendel, the 5.56 NATO would have shown even poorer performance.

  • Where the 6.5 Grendel hidden gem shines is for PSD. Compare it to the 5.56 out of 12" barrels. The 6.5 is better at 300m than the 5.56 at 100m. I'd love to see it become more popular.

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