The AR-15 vs AK-47 discussion will most of the time lead to the 6.5 Grendel vs 7.62×39 question.
The AK-47 is confined to using the only bullet it was made for. In contrast, the AR-15 is a much more multipurpose rifle.
Replace the barrel and bolt and upper receiver on the AR-15 and one can use all types of cartridges, including the 6.5 Grendel.
Which Comes Out On Top in a 6.5 Grendel vs 7.62×39 Comparison
The 6.5 Grendel traces its creation to the year 2003 to beat the 5.56×45. Its original case is the 220 Russian, a derivative from a narrowed down 7.62×39.
The 6.5 Grendel and 7.62×39 have very many similarities.
The 7.62×39 is around 1/5” shorter in length and has close to a similar volume for propellant. It has practically the same length as the case compared to the 6.5 Grendel.
Differences of the 6.5 Grendel vs 7.62×39
The 7.62×39 uses a .30 caliber bullet, and the 6.5 Grendel’s uses a 6.5mm bullet that is narrower. Both are usually the same weight at 123 grains.
The 6.5 Grendel comes in bullet weights from 90 to 129 grains, however, for comparison, we will look at rounds with comparable bullet weights to the 7.62×39.
Brands usually load the 6.5 Grendel to a higher pressure. As such, it can deliver a more powerful muzzle velocity than the 7.62×39.
Gun owners praise the 6.5mm bullet for its excellent high ballistic coefficient. It provides superior long-distance precision against the 7.62×39.
Its all-out range is said to be 800 yards while the 7.62×39 is about 400 yards.
A look at the ballistic results shows more data. The 6.5 Grendel’s quicker muzzle velocity fights gravity by providing less time to propel it downward. This results in a more level trajectory.
Likewise, the 6.5 Grendel does not change to subsonic (1,125 fps) until very far in its travel.
Although similar in weight to the 7.62×39, the 6.5 Grendel’s narrower bullet shape has much less wind drag. Its superior ballistic coefficient shows this.
The higher ballistic coefficient likewise gives the 6.5 Grendel superior characteristics to the effects of vertical and horizontal crosswinds. This matters a lot during long-distance targeting.
While the 6.5 Grendel is more precise, the 7.62×39 is not bad at all. It can hit targets even though these are shorter distances of about 200 yards where it excels.
Comparing Stopping Power
For stopping power the 6.5 Grendel is superior to the 7.62×39. This is owing to sectional energy and density.
Sectional density is how effectively a bullet pierces soft tissue. Bullet weight and diameter are two key factors that affect sectional density.
Since the two bullets weigh 123 grains, the diameter is the only aspect that decides which has better sectional density.
The narrower 6.5 Grendel bullet fights less resistance from soft tissue compared to the wider 7.62×39.
The Grendel sectional density is 0.252 while the 7.62×39’s is 0.184, thus penetrating targets deeper.
Recoil is the kickback you get when you shoot a firearm. Less recoil means more comfort when shooting, and reduced muzzle flip that affects the time to restore your aim.
Another benefit is effective multiple targets in fast bursts, whether for hunting or in a self-defense scenario.
A typical 7.62×39 cartridge measured 7.05 ft.-lbs. of recoil power. The typical 6.5 Grendel cartridge measures 7.93 ft.-lbs. Those numbers are hardly noticeable indifference.
There is no reason to favor one round over the other as far as their recoil is concerned.
Price and Availability
Both cartridges are not difficult to source. The 7.62×39 is quite popular since it has been around for over half a century more than the 6.5 Grendel.
AK-47s were produced massively and are easy to acquire. On the other hand, one can modify any AR-15 to use a newer round with a conversion kit.
Hence, arguably there are more rifles chambered for the 6.5 Grendel in theory.
The 7.62×39 costs less since it is manufactured in high numbers. The 6.5 Grendel, however, is of higher quality than long-distance shooters love.
The Verdict: 6.5 Grendel vs 7.62×39
The 7.62×39 is a durable and hard-to-beat cartridge.
Its precision and easy-to-handle recoil as well as immense power at near to medium range are great attributes for home defense scenarios.
In hunting, however, its performance is inferior compared to larger cartridges. Its legions of fans though, still love to fire it.
The 6.5 Grendel is capable of all the 7.62×39 abilities.
Its compatibility with the AR-15 platform makes it the first pick for long-distance targets. It has excellent stopping power at medium to long range.
The 6.5 Grendel vs 7.62×39 comparison comes down to what you need. If you want to shoot buckets of rounds into targets for a few hours, it is the the7.62×39 for you.
However, if you desire a more textbook long-distance shooting experience, the 6.5 Grendel is the way to go.