The 5.56×45 is the king of American rifle cartridges. We doubt a new round will ever come along to dethrone it – it works great, and too many millions of AR-15s are already chambered for 5.56.

But plenty of alternative cartridges have been introduced for the AR-15 platform in recent years. In order to earn some share of the ammo market, these rounds have to offer something different enough from the 5.56 to grab shooters’ attention.

The 6.5 Grendel is one of these newer AR-15 rounds. It certainly looks different enough from 5.56 ammo with its lower shoulder and longer bullet, but what exactly does it do differently that merits its popularity? We’re going to compare the two rounds’ ballistics, energy, and recoil to see if there’s a clear winner to the 5.56×45 vs. 6.5 Grendel debate, or if they each offer their own distinct advantages.

Cartridge Dimensions

6.5 Grendel vs 5.56 ammunition side by side

 5.56x456.5 Grendel
Parent case223 Rem220 Russian
Case typeRimless, bottleneckRimless, bottleneck
Bullet diameter0.224 in0.264 in
Neck diameter0.253 in0.293 in
Shoulder diameter0.354 in0.428 in
Base diameter0.377 in0.439 in
Rim diameter0.378 in0.440 in
Case length1.760 in1.520 in
Overall length2.260 in2.260 in
Case capacity28.5 gr H2O35.0 gr H2O
Maximum pressure62,366 psi52,000 psi

Right away you will notice that the 5.56 and 6.5 Grendel have different diameter bullets: 0.224” vs. 0.264”. We can expect this disparity to impact the rounds’ in-flight ballistics.

The 6.5 Grendel’s larger case has capacity for about 22 percent more propellant. Its wider bullet often weighs over twice as much, though. This means we should still expect it to deliver a slower muzzle velocity.

As a side note, it is interesting to note that the two rounds share the same exact length. Even though 5.56 magazines will hold 6.5 Grendel cartridges, they don’t work reliably enough to be considered compatible with 6.5 Grendel lower receivers. As such you’ll still need a dedicated 6.5 Grendel magazine.

6.5 Grendel vs. 5.56 Ballistics

Muzzle Velocity

Measuring 5.56 velocity with a chronograph at a shooting range with an AR-15

 5.56 Fed. American Eagle 55 Gr6.5 Grendel Hornady Frontier 123 Gr FMJ5.56 Hornady Superformance Match 75 Gr6.5 Grendel - Hornady BLACK 123 Gr5.56 Federal Tactical Bonded 62 Gr6.5 Grendel Federal Fusion 120 Gr
Muzzle velocity (fps)316525802910258030502600
Velocity @ 100 yds277723772674241226372349
Velocity @ 200 yds242121832451225122602113
Velocity @ 300 yds209219982238209619151891
Velocity @ 400 yds179118242036194816071685
Velocity @ 500 yds152316601845180613451498
Velocity @ 600 yds129715091667167211471333
Velocity @ 700 yds112813721504154610201197
Velocity @ 800 yds10171253135814299371093
Velocity @ 900 yds9411155123213248731018
Velocity @ 1000 yds882107811311230820961

It is interesting to note that the 6.5 Grendel has a slower muzzle velocity than the 5.56. This means you will have to arc its trajectory more in order to hit your target. However, because the 6.5 Grendel bullet is significantly heavier and has a higher ballistic coefficient (a measure of ability to overcome air resistance in flight, where a higher number is better), it is able to retain more of its initial velocity at farther distances downrange. The 6.5 Grendel often offers higher velocities than the 5.56 beyond 400 yards in spite of its slower start.

Trajectory

 5.56 Fed. American Eagle 55 Gr6.5 Grendel Hornady Frontier 123 Gr FMJ5.56 Hornady Superformance Match 75 Gr6.5 Grendel - Hornady BLACK 123 Gr5.56 Federal Tactical Bonded 62 Gr6.5 Grendel Federal Fusion 120 Gr
Elevation @ 100 yds7.299.377.198.818.5210
Elevation @ 200 yds11.5314.0510.9913.1113.4815.14
Elevation @ 300 yds9.7811.418.9810.5311.5612.47
Elevation @ 400 yds0.020.0300.030.050.02
Elevation @ 500 yds-20.68-21.83-17.39-19.65-25.08-24.73
Elevation @ 600 yds-56.5-56.35-45.03-50.02-69.57-65.03
Elevation @ 700 yds-113.06-106.18-85.21-92.86-140.47-124.95
Elevation @ 800 yds-196.92-174.52-140.82-150.27-244.89-209.15
Elevation @ 900 yds-314.54-265.02-215.34-224.73-388.71-322.61
Elevation @ 1000 yds-471.2-381.79-312.77-319.06-578.38-469.4
G1 ballistic coefficient0.250.4270.3950.520.2280.346
G7 ballistic coefficient0.1260.2160.2010.2610.1170.177

Its greater momentum and resistance to wind deflection make the 6.5 Grendel a lot more useful for hitting targets up to 800 yards out. It can even be pushed past 1,000 yards with practice. The 5.56 can hit 1,000 yards too. However, the general consensus is that it’s not really all that effective beyond 300 yards.

Because it offers greater accuracy over longer distances, the 6.5 Grendel is the more sniper-friendly cartridge.

Energy

The amount of energy a bullet can transfer to its target depends entirely on two factors: mass and velocity. The faster or heavier a bullet becomes, the more damage it’s inclined to inflict on impact.

The 6.5 Grendel bullet spends its first 300 to 400 yards moving slower than the 5.56. It often weighs more than twice as much, however, so it carries superior energy at all ranges.

 5.56 Fed. American Eagle 55 Gr6.5 Grendel Hornady Frontier 123 Gr FMJ5.56 Hornady Superformance Match 75 Gr6.5 Grendel - Hornady BLACK 123 Gr5.56 Federal Tactical Bonded 62 Gr6.5 Grendel Federal Fusion 120 Gr
Muzzle energy (ft lbs)122418181410181812811802
Energy @ 100 yds9421543119115909571471
Energy @ 200 yds7161302100113857031190
Energy @ 300 yds53510918341201505953
Energy @ 400 yds3929086911036355757
Energy @ 500 yds283753567891249598
Energy @ 600 yds205622463763181474
Energy @ 700 yds155514377653143382
Energy @ 800 yds126429307558121318
Energy @ 900 yds108364253478105276
Energy @ 1000 yds9531721341493246

Either cartridge would prove more than adequate for varmint hunting or self-defense. Personal protection generally calls for a minimum foot-pound force of 220 to 300. Although the 5.56 typically dips beneath that threshold by 600 yards, it is highly unlikely that you will have to engage a threat at so great a distance.

The 6.5 Grendel’s greater energy does make it the better choice for deer hunting, though. A foot-pound force of 1,000 or greater is recommended for the ethical hunting of whitetail. The 5.56 can fall beneath this threshold by as short as 100 yards, though the 6.5 Grendel consistently puts 1,000 ft lbs or more energy on target beyond 300 yards – and often farther.

6.5 Grendel vs 5.56: Recoil

The ideal rifle would generate zero recoil energy when fired. The ideal rifle doesn’t exist, so you’re always going to have to put up with at least some kick.

It is impossible to calculate the exact amount of recoil you will actually feel. That is determined in part by your own nervous system, the details of which we don’t have access to.

But we can fairly estimate a cartridge’s recoil energy by weighing four known factors: rifle weight, propellant weight, bullet weight and muzzle velocity. For the purpose of calculating the recoil energy of the six cartridges compared above we’ll assume all 5.56 rounds have 24 grains of propellant and all 6.5 Grendel rounds have 30. We’re also firing 7.5 lb rifles.

 Recoil Energy (ft lbs)
5.56x45 Federal American Eagle 55gr FMJBT3.66
5.56x45 Hornady Superformance Match 75gr ELD Match4.84
5.56x45 Federal Tactical Bonded 62gr SP4.04
6.5 Grendel Hornady Frontier 123 gr FMJ9.24
6.5 Grendel Hornady BLACK 123 gr ELD Match9.24
6.5 Grendel Federal Fusion 120 gr SP9.03

While the 6.5 Grendel’s muzzle velocity is slower across the board. Plus, in all cases its significantly heavier bullet is enough to generate more than double the 5.56’s recoil energy.

Neither round’s recoil energy is enough to make an average sized shooter uncomfortable. The 6.5 Grendel’s heavier recoil simply makes rapid, accurate fire more difficult. The 6.5 Grendel’s steeper muzzle rise will increase the amount of time you have to spend restoring your aim following every time you fire. If your goal is to shoot two targets in rapid succession, or put as many bullets into a target as quickly as possible (as you would for self-defense) then the 6.5 Grendel’s heavier recoil will make that goal more difficult.

Availability & Price

The 5.56 beats pretty much every other centerfire rifle cartridge in terms of availability. Alongside the 223 Rem, which a rifle chambered for 5.56 can fire interchangeably, it is the most popular rifle round in America.

The 6.5 Grendel has certainly found a market since its introduction in 2004. You should find plenty of options – just nowhere near as many as you would while shopping for 5.56.

The 5.56 is the cheaper cartridge. There’s a greater market for it, and as the smaller round it demands fewer raw materials for its production. The 6.5 Grendel is not very far behind, though. Russia’s steel-cased 6.5 Grendel ammo costs almost as little as target-grade brass-cased 5.56, and it’s often cheaper than 308 Win.

The 6.5 Grendel isn’t so niche that building an AR-15 chambered for it is significantly more expensive, either. All in all, the cost difference between the two rounds isn’t great enough to become the determining factor as to which you should prefer.

Grendel vs. 5.56×45: The Takeaway

The 5.56 has a flatter trajectory than the 6.5 Grendel. But remember, its long-distance performance can’t compare to its competitors heavier, more ballistically efficient bullet. The 6.5 Grendel is the better long-range round.

The 6.5 Grendel delivers far more energy to its target at all ranges. Although either cartridge is well equipped for self-defense, the 6.5 Grendel’s better suitability for deer hunting is not up for debate.

The 6.5 Grendel’s superior in-flight and terminal ballistics come at a price: greater recoil energy. You may feel twice as much kick while firing the newer round. The biggest drawback of that is greater difficulty when it comes to rapid fire.

Though many aspects of the 5.56’s performance are inferior to those of the 6.5 Grendel, it is by no means a poor cartridge. So, in this debate between 6.5 Grendel vs 5.56, if you were to pick only one round to use exclusively, we would have to recommend America’s longtime favorite.

But if you’re interested in getting better long-range performance out of the AR-15 platform, the 6.5 Grendel is a great way to go!