Among endlessly many hot topics for AR-15, the comparisons of calibers compatible with AR platform rifles always attract a lot of attention.
Unlike calibers from different sides of the power spectrum, comparing cartridges with similar ballistics is quite challenging and requires extensive work with more profound research and presenting data in tables for better explanation.
For those who prefer a modern or tactical rifle rather than a more traditional rifle, there is a wide choice of cartridges compatible with AR-style or similar semi-automatic rifles.
| Cartridge | 6.5 Grendel | 223 Remington |
| Bullet | 90 gr to 130 gr (6.0 to 8.0 g) | 36 gr to 77 gr (2.0 to 5.0 g) |
| Bullet diameter | 0.264” (6.7 mm) | 0.224” (5,7 mm) |
| Case length | 1.52” (38.6mm) | 1.76” (44.7 mm) |
| Maximum overall length | 2.26” (57.4 mm) | 2.26” (57.4 mm) |
| Rim diameter | 0.44” (11.1 mm) | 0.378” (9.6 mm) |
| Max Pressure (SAAMI) | 52,000 psi | 55,000 psi |
| Muzzle Velocity | 123 gr/ 2,580 fps | 55 gr/ 3,240 fps |
| Muzzle Energy | 123 gr/ 1,818 ft-lbs. | 55 gr/ 1,282 ft-lbs. |
| 400yds Bullet Drop & Energy | -26.4” 1,027 ft-lbs. | -21.4” 428 ft-lbs. |
| Powder load | 26.0 gr | 24.0 gr |
| Rifle Weight | 6.6 lbs. | 6.0 lbs |
| Free recoil energy | 125gr/10.3 ft-lbs. | 55gr/4.45 ft-lbs. |
| Case capacity | 35.0 gr H2O | 28.5 gr H2O |
Main Contents
6.5 Grendel
In an attempt to find a better alternative to the official NATO .22 caliber round, many ammo makers, gun enthusiasts and handloaders experimented with larger calibers. The 5.56/.223 Remington was intended for use in AR-15 and designed for close-quarter battles of the second half of the 20th century. However, modern battlefields require something heavier with a more extended range and more power but wrapped in a more compact package than full-power calibers such as .308 Winchester/7.62 NATO.
Actually, the 6.5 Grendel is in a golden middle between the .223 Rem and the .308 Win cartridges. As an extremely versatile cartridge, Grendel will work well for close-quarter battles, but at the same time, it will reliably take out the medium-sized game at 400 to 500 yards. In fact, at the 600 – 700-yard range, the Grendel will have over twice the retained energy compared to the .223 Remington.
One of the best and most popular alternatives to the .223/5,5×45 is the 6.5 Grendel cartridge released in 2003 by Alexander Arms LLC, Arne Brennan, competitive shooter and Janne Pohjoispää, a ballistician from Finish Lapua. Along with the medium bore 6.5 Grendel cartridge, the owner and chief designer of the company, Bill Alexander, also developed a big bore option to the .223 Rem/5.56x45mm NATO known as .50 Beowulf.
When the military started looking for a new cartridge, a basic idea for development was to design a round of the same overall length of 5.56mm/ .223 Remington. The new cartridge should fit in the relatively tight constraints of the AR-15 platform, including the rifle action and magazine.
The 6.5 Grendel is an intermediate cartridge based on the Russian 7.62×39 and was developed initially for military and tactical applications.
Using the 6.5mm PPC as its parent case, the 6.5 Grendel is actually the far cousin of the 7.62×39 Kalashnikov. in order to make things more clear, the mentioned PPC cartridge has descended from the .220 Russian, a Russian sub-caliber version of the Soviet M43, a 7.62×39 cartridge.
However, civilian gun enthusiasts such as long-range target shooters and hunters soon recognized the advantages of the aerodynamic 6.5mm bullet and adopted it in a short time.
Generally, the .264 caliber bullet has a very high ballistic coefficient and sectional density, making it an ideal competitor for maximizing the efficiency of AR ammunition between 200-800 yards.
Regarding its civilian applications, the 6.5 Grendel has demonstrated remarkable effectiveness for hunters and its excellent range of bullet weights. In terms of a distance of 100 yards, the Grendel delivers approximately 600 ft-lbs and more energy to the target than the .223 Remington.
With a clear edge over the .223 Remington, 6.5 Grendel can effectively engage targets up to over 400 yards and deliver more energy on target at most ethical hunting ranges.
As an alternative to a mainstream option, the 6.5 Grendel has a limited number of loads and bullet types. For the rifles chambered in 6.5 Grendel, ammo manufacturers make rounds that use bullets in the 90-140 grain range, but most widespread are 100, 110, 120 and 123-grain bullets.
The 6.5 Grendel fires a 120-grain bullet at 2,600 fps and generates about 1,800 foot-pounds of energy. Another typical load of 123-grain bullet fired at 2,580 fps from the muzzle will have 1,000 foot-pounds kinetic energy at 400 yards, which is considered the minimum for a lethal terminal performance on the deer-sized game.
Conversely, the majority of .223 Remington factory loads fire bullets in the 35-90 grain range. The most common bullet weights available are 55-grain, 62-grain and 77-grain. Typical, commercial .223 Remington ammo loaded with 55-grain bullet leaves the 20-inch barrel at approximately 3,240 feet per second and produces 1,282 ft-lbs of muzzle energy.
Compared to the .223 Remington/ 5.56x45mm NATO, the 6.5 Grendel, using significantly heavier bullets, carries more energy downrange and provides more room for error in shot placement.
The .223 Rem is well known for its almost nonexistent recoil, but the major selling point of the 6.5 Grendel also is a reduced recoil. Even though the .223 Rem is the king of low-recoil cartridges since it generates about 50% less recoil than the Grendel, in a 6.6-pound rifle, a Grendel 125-grain load will churn over inc10 feet-pounds of recoil energy that’s about twice more kick than a .223 Remington driving a 55-grain bullet.
Of course, it doesn’t mean you will have any problem with handling a 6.5 Grendel when it comes to recoil management. On the other side, if you are a smaller body shooter or recoil-shy hunter, the barely noticeable recoil of the .223 Remington will be a superior choice for better accuracy and quicker follow-up shots.
Compared to other .223 alternative cartridges for use on the AR-15 platform, the Grendel will only require a barrel, and a different bolt (bolt carrier group), while many recommend a specific magazine.
.223 Remington
While the .308 Winchester was created to replace the venerable .30-06 Springfield cartridge and M-1 Garand rifle, the .223 Remington was designed in 1957 and introduced in 1963 for use in a new service rifle called AR-15.
Designed as a combat round, the main task of .223 was to deliver enough stopping power to neutralize a human-sized target up to 500 yards. Using .223 Rem as a commercial cartridge with hollow points, hunters can expect to take out a medium-sized game at 250 yards reliably.
Even though both the .223 Remington and the 6.5 Grendel cartridges are designed for AR-15 weapons, there are significant differences between each.
Compared to .223 Rem, the 6.5mm Grendel has the same overall length but is fatter and has a larger projectile.
Moreover, the 6.5 Grendel has a rim diameter of .441 inches which is larger than the .223 Rem, which comes in at .378 inches.
While the Grendel has a slightly larger case capacity than .223, in terms of maximum average pressure between the two, the .223 Rem is loaded higher. It comes in at 55,000 psi (379 MPa) against 52,000 psi (358 MPa) of the 6.5 Grendel.
The 6.5 Grendel is designed to provide more power at a longer range than the .223 Remington so that it could be used for big game hunting.
There is no argument that the .223 Remington is faster than Grendel, and with common 55-grain bullets, it is 600 fps (feet per second) faster than 6.5 Grendel with the standard 120-grain loads.
From a financial aspect, the 223 Remington is an economical cartridge compared to the 6.5 Grendel. The new basic ammo for .223 is around $0.68 per round vs. $1.5 per round for 6.5 Grendel.
Final thought
While both cartridges are compatible with an AR-15 platform, the 6.5 Grendel offers a few notable benefits above the .223 Remington.
As a legitimate alternative to the 5.56mm, the 6.5 Grendel is tailored to a new role on the battlefield, but today it is a perfect all-around cartridge for people who like the AR-15 platform.
Whether you need it for self-defense/personal protection, a medium-size game, or target shooting, the 6.5 Grendel is also a really nice choice, with a very good barrel life of 4,000 to 5,000 rounds.
On the other side, the .223 Remington is the more popular round due to the widespread military deployment, affordable ammo, and straight shooting without recoil.
In terms of small game hunting, Grendel cannot beat a .223 Rem because 6.5 Grendel packs way too much punch and more cost per round.
Though both cartridges are designed to fit an AR-15 action, the difference between them is pretty big in certain respects. It means that each of them is better suited to specific situations than the other.
In the end, deciding which one you should add to your personal collection depends on your needs, shooting style and budget.
Travis Mike is a firearm enthusiast and author passionate about all things guns. With 10 years of experience in the industry, Travis Mike has gained a wealth of knowledge on the subject. He is skilled in gunsmithing and tactical training. In addition to professional experience, Travis Mike is an avid hunter and shooter, regularly participating in local shooting ranges and hunting trips.