The AK-47 vs. AR-15 debate often boils down to the 7.62×39 vs. 5.56/223 debate. Yet while the AK-47 is limited to firing the only cartridge it was originally designed for, the AR-15 is a far more versatile rifle. A new upper receiver, barrel and bolt will let you fire all kinds of different cartridges – the 6.5 Grendel included. So, who wins in a 7.62×39 vs 6.5 Grendel debate?

The 6.5 Grendel was designed in 2003 to surpass the performance of the 5.56×45. Interestingly enough its parent case is the 220 Russian, which itself was derived from a necked down 7.62×39. But we’re not interested in cartridge histories. We want to compare these two rounds’ ballistic performance, stopping power and recoil to see if the 6.5 Grendel is indeed significantly better than the 7.62×39. And what does “better” mean in this context?

Cartridge Dimensions

6.5 grendel vs 7.62x39 ammo side by side

 7.62x396.5 Grendel
Case typeRimless, bottleneckRimless, bottleneck
Bullet diameter0.309-0.311 in0.264 in
Neck diameter0.339 in0.293 in
Shoulder diameter0.396 in0.428 in
Base diameter0.447 in0.439 in
Rim diameter0.447 in0.44 in
Rim thickness0.059 in0.059 in
Case length1.524 in1.52 in
Overall length2.205 in2.26 in
Case capacity35.6 gr H2O35 gr H2O
Maximum pressure45,010 psi52,000 psi

The 7.62×39 and 6.5 Grendel share remarkably similar dimensions. The 7.62×39 is less than 1/5” shorter in overall length, has nearly the same capacity for propellant, and has virtually the same case length as the 6.5 Grendel.

But these rounds are far from carbon copies of one another. 7.62×39 ammo has a .30 caliber bullet, whereas the 6.5 Grendel’s 6.5mm bullet is a good deal narrower. Either rounds’ bullets are commonly the same weight at around 123 grains, however, making the 6.5 Grendel’s bullet necessarily longer. (The 6.5 Grendel offers bullet weights ranging from 90 to 129 grains, but for the sake of comparison we’re focusing on rounds with similar bullet weights to what the 7.62×39 can offer.) Manufacturers load the 6.5 Grendel to a higher pressure. So, we can reasonably expect it to deliver a greater muzzle velocity than its Russian competitor.

6.5 Grendel vs. 7.62×39: Ballistic Comparison

Velocity

Firing a 6.5 Grendel rifle at a shooting range

 7.62x39 Federal Fusion 123gr SP6.5 Grendel Federal Fusion 120gr SP7.62x39 Prvi Partizan 123gr SP6.5 Grendel Prvi Partizan 123gr SP7.62x39 Hornady BLACK 123gr SST6.5 Grendel Hornady Custom 123gr SST
Muzzle velocity (fps)235026002461265723502580
Velocity @ 50 yds221324732254253121942495
Velocity @ 100 yds208023502057240920442413
Velocity @ 150 yds195222301871229019002331
Velocity @ 200 yds182921131697217517632251
Velocity @ 250 yds171220001536206216342173
Velocity @ 300 yds160118911390195415132096
Velocity @ 350 yds149617861263184914012021
Velocity @ 400 yds139916851158174713001948
Velocity @ 450 yds131015891077165112121876
Velocity @ 500 yds123114981016155811381806
Velocity @ 550 yds11621413967147110781738
Velocity @ 600 yds11041333926138910291672
Velocity @ 650 yds1057126189013139881608
Velocity @ 700 yds1017119785812459531546
Velocity @ 750 yds982114182811849231486
Velocity @ 800 yds952109380111318951429

Shooters love the 6.5mm bullet for its relatively high ballistic coefficient. The 6.5 Grendel certainly offers superior long-distance accuracy over the 7.62×39. Its maximum range is generally considered to be 800 yards; the 7.62×39, on the other hand, is about half that.

A cursory glance at our ballistic data reveals why that is. The 6.5 Grendel’s faster muzzle velocity gives gravity far less time to pull its bullet down. This conveys a flatter trajectory, which doesn’t necessarily impart better accuracy – but it sure does help a lot. The 6.5 Grendel also doesn’t transition to subsonic (1,125 fps) until much farther in its trajectory.

7.62×39 vs 6.5 Grendel Trajectory

 7.62x39 Federal Fusion 123gr SP6.5 Grendel Federal Fusion 120gr SP7.62x39 Prvi Partizan 123gr SP6.5 Grendel Prvi Partizan 123gr SP7.62x39 Hornady BLACK 123gr SST6.5 Grendel Hornady Custom 123gr SST
Elevation @ 50 yds4.053.434.083.314.143.33
Elevation @ 100 yds4.83.924.933.764.963.75
Elevation @ 150 yds3.542.843.712.713.72.68
Elevation @ 200 yds00.010.0100.020.01
Elevation @ 250 yds-6.14-4.77-6.72-4.55-6.46-4.37
Elevation @ 300 yds-15.25-11.73-17.15-11.15-16.2-10.6
Elevation @ 350 yds-27.76-21.12-32.09-20.02-29.75-18.8
Elevation @ 400 yds-44.15-33.23-52.49-31.44-47.73-29.14
Elevation @ 450 yds-64.99-48.41-79.37-45.72-70.85-41.76
Elevation @ 500 yds-90.9-67.03-113.72-63.18-99.9-56.86
Elevation @ 550 yds-122.55-89.54-156.49-84.23-135.66-74.62
Elevation @ 600 yds-160.63-116.39-208.56-109.3-178.9-95.27
Elevation @ 650 yds-205.83-148.14-270.99-138.88-230.33-119.02
Elevation @ 700 yds-258.82-185.36-344.19-173.49-290.66-146.14
Elevation @ 750 yds-320.42-228.64-429.2-213.72-360.79-176.89
Elevation @ 800 yds-390.82-278.6-527.19-260.14-440.89-211.58

Despite having essentially the same weight as the 7.62×39, the 6.5 Grendel’s narrower bullet encounters significantly less air resistance in flight. Its higher ballistic coefficient reflects this. Its higher ballistic coefficient also grants the 6.5 Grendel greater resistance to the straying effects of cross and vertical winds, which comes heavily into play in long-distance shooting.

So the 6.5 Grendel, which has a greater muzzle velocity and higher ballistic coefficient, is more accurate over longer distances. However, the 7.62×39 can not be described as inaccurate. It is perfectly capable of hitting its target, albeit over the shorter ranges it was designed to cover. Within 200 yards the 7.62×39 is great!

Stopping Power

The 6.5 Grendel has greater stopping power than the 7.62×39. This is due to a couple key factors: sectional density and energy.

“Sectional density” is a technical term that describes how efficiently a bullet penetrates soft tissue. Two variables determine sectional density: bullet weight and diameter. Obviously when both bullets weigh 123 grains, their diameters become the only factor that determines which has the superior sectional density. Simply put, the narrower 6.5 Grendel bullet encounters less resistance from soft tissue than the wider 7.62×39. Its sectional density is 0.252 as opposed to the 7.62×39’s 0.184, so it is equipped to penetrate its target deeper.

The amount of energy a bullet can transfer to its target depends on its weight and velocity. Once again, only the bullets’ velocities come into play when their weights are the same. The 6.5 Grendel’s greater muzzle velocity quite naturally means its bullet is moving faster than the 7.62×39’s at all points downrange. Furthermore, its higher ballistic coefficient also means it retains relatively more of its velocity.

 7.62x39 Federal Fusion 123gr SP6.5 Grendel Federal Fusion 120gr SP7.62x39 Prvi Partizan 123gr SP6.5 Grendel Prvi Partizan 123gr SP7.62x39 Hornady BLACK 123gr SST6.5 Grendel Hornady Custom 123gr SST
Muzzle energy (ft lbs)150918021654192815091818
Energy @ 50 yds133716301654175013141701
Energy @ 100 yds118214711156158511411590
Energy @ 150 yds1041132595614339861485
Energy @ 200 yds914119078612928491385
Energy @ 250 yds801106664411627291290
Energy @ 300 yds70095352810436251201
Energy @ 350 yds6128504369335361116
Energy @ 400 yds5357573668344621036
Energy @ 450 yds469673317744401961
Energy @ 500 yds414598282663354891
Energy @ 550 yds369532255591317825
Energy @ 600 yds333474234527289763
Energy @ 650 yds305424216471267706
Energy @ 700 yds282382201423248653
Energy @ 750 yds264347187383233604
Energy @ 800 yds248319175349219558

For self-defense the difference in these two rounds’ stopping power isn’t all that crucial. We highly doubt you would engage a threat at distances beyond 100 yards, and the stopping power of either round is beyond adequate to neutralize a human-sized threat at close range.

For hunting the disparity in stopping power becomes more important. To make matters extremely simple, a bullet would ideally deliver at least 1,000 ft lbs of energy to humanely kill a whitetail. The 7.62×39 often fails to deal that much damage at 150 yards, yet the 6.5 Grendel consistently exceeds 1,000 ft lbs at 300 yards. Deer hunters unquestionably prefer the 6.5 Grendel.

Recoil

We’re sure you’re well aware of what recoil is. Its the kickback you feel whenever you fire a weapon, and the reason why you wouldn’t let little Timmy shoot your 700 Nitro Express elephant gun. The recoil would send the poor bugger flying over the rooftops.

Lower recoil offers two key benefits: more comfortable shooting, and less muzzle flip that increases the amount of time it takes to restore your aim in between shots. The second benefit is crucial for shooting multiple targets in quick succession, whether you’d do so for hunting or in self-defense.=

We’re going to compare the recoil generated by the six rounds detailed above. It is easy to calculate a cartridge’s recoil energy with just four data points: bullet weight, propellant weight, muzzle velocity and rifle weight. For convenience’s sake we’re realistically assuming all rounds have 24 grains of propellant and both rifles weigh 7.7 pounds.

 Recoil Energy (ft lbs)
7.62x39 Federal Fusion 123gr SP6.89
7.62x39 Prvi Partizan 123gr SP7.36
7.62x39 Hornady BLACK 123gr SST6.89
6.5 Grendel Federal Fusion 120gr SP7.69
6.5 Grendel Prvi Partizan 123gr SP8.22
6.5 Grendel Hornady Custom 123gr SST7.88

The average 7.62×39 cartridge generates 7.05 ft lbs of recoil energy. The average 6.5 Grendel cartridge generates 7.93 ft lbs. That difference is negligible. There is no reason to favor one round over the other as far as their recoil is concerned.

Bear in mind that heavier bullets, faster muzzle velocities, and lighter rifles are all going to result in heavier recoil. Also, the amount of recoil you’ll actually perceive is subjective. No amount of math can predict what you’re going to feel.

Availability & Price

An AK-47 rifle that fires 7.62x39 ammo

Neither the 7.62×39 or the 6.5 Grendel are niche cartridges that you’ll have trouble finding. The 7.62×39 certainly wins in a popularity contest, though. It’s been around for about 60 years longer than the 6.5 Grendel, and while you would have found few American 7.62×39 fans back in the ‘50s it is extremely popular now.

AK-47s are abundant. I bought a gently used Century Arms C39V2 with four magazines from a guy I met in a parking lot for $500 back in 2017. It seems gun prices will continually go up, but you can still get a serviceable AK without breaking the bank.

The 6.5 Grendel is a different story. You can convert any AR-15 to run the newer round with a conversion kit, so you can argue that there are more rifles chambered for it – potentially speaking.

The two rounds’ price tags aren’t dramatically different. The 7.62×39 is indeed cheaper, if only because it’s produced in higher quantities and 6.5 Grendel ammo tends to be of the higher quality that long-distance shooters demand. You also have to consider the great abundance of Russian-made steel-cased 7.62×39 on the market as well. It’s not match ammo by any stretch of the imagination, but for the kind of plinking that AK enthusiasts love it serves nicely. Manufacturers like Wolf offer steel-cased 6.5 Grendel as well, but again, it’s hardly ideal if you’re aiming for 800 yard targets.

The Takeaway: 7.62×39 vs 6.5 Grendel

The 7.62×39 is a workhorse of a cartridge. Its manageable recoil, decent accuracy and crushing energy at close to medium range all make it more than enough to count on for home defense. Its performance for hunting is lacking in comparison to larger cartridges. However, it’s just so fun to shoot that you may not want it for any place other than the range.

The 6.5 Grendel does everything the 7.62×39 does – only better. That’s an oversimplification, although its compatibility with the AR-15 platform (which isn’t to deny the existence of the AR-47), suitability for long-distance shooting, and far greater stopping power at medium to long range are all available from the 6.5 Grendel if you want them. You’ll pay more for ammo, but less for a rifle if you simply convert your AR-15 to chamber the newer round.

The 7.62×39 vs 6.5 Grendel debate does largely boil down to what you want to do with a rifle. If that’s dumping a case worth of ammo into plinking targets over the course of a few hours, go Russian. But if you want to enjoy somewhat more technical long-distance shooting, in this case you’ll want to go American.