The 6.5 Grendel has more velocity, range, and more energy than 300 Blackout. The Blackout works well with subsonic loads in a pistol-length barrel, but has a short effective range. Both fit in an ar-15 and have low recoil. The 6.5 Grendel has more utility while the 300 Blackout was designed to work quietly in short barrels.
There is a world of difference between these two cartridges. They both have very specific uses and your personal needs will probably make the decision for you.
30 Caliber vs 26 Caliber
The 300-Blackout is a lower-power 30-caliber cartridge. The 6.5 Grendel is a lower to mid-power 26 caliber cartridge. Most bullets from both cartridges weigh around 125-Grains. Because the Blackout is wider, yet they tend to have similar weight, the Blackout has a lower Ballistic Coefficient than the 6.5 Grendel.
There is a notable difference between the 30 calibers and 26 caliber diameter, especially after bullet expansion. The 30-caliber 300-Blackout will tend to make a wider hole, but it won’t penetrate as much as a comparable bullet in 6.5 Grendel.
30-caliber (.308 actually) is a common bullet size, so there’s a wider selection of available bullets for the Blackout both in factory ammo and for reloading. The .264 bullets used in the Grendel are less common, so there’s less of a selection to choose from. But, there’s still great bullets for both
Expansion and Velocity
The Blackout is a slow cartridge, and velocity is what causes bullet expansion. Most bullets fail to expand at velocities under 1800 fps. That’s about 125-yards for most supersonic Blackout loads. The Grendel is generally functional to 400-Yards before it gets too slow to reliably expand.
The 300 Blackout really tends to lack expansion compared to the Grendel, but it still seems to work well enough on deer and hogs at 100-yards. It’s one of the popular AR cartridges for hog hunting. Most hog hunters try to keep their shots within 100-yards, but some will shoot 150-yards. 200-yards is just too far for the Blackout.
As a bullet slows down, it expands less and less until it doesn’t expand at all. At 100-yards, Blackout hunting loads are only expanding a very little bit. Not that that’s a reason t throw it out, it’s just a short-range rifle.
The Blackout’s shorter and fatter design sheds energy faster (has more drag) than the slimmer Grendel bullet, and it starts out with significantly less power. The Grendel was developed for general hunting and military use to 400-yards, but the Blackout was designed primarily for tactical use with a suppressor within 100-yards.
6.5 Grendel is More Powerful Than 300-Blackout
6.5 Grendel Has 40 percent more initial bullet energy and 400 fps more velocity than the 300-Blackout given similar weight bullets. Common 123 grain 6.5 Grendel loads are faster and more powerful than the 125-grain 300-Blackout loads.
The best comparison of two different cartridges is with a similar weight and style of bullets. Fortunately, we can do that here. The most common 6.5 Grendel bullet weight is 123-grains. the most common 300-Blackout bullet weight is 125-grains.
Here is the data from Hornady’s FRONTIER line of ammo comparing a 123-grain fmj 6.5 Grendel and a 125-grain fmj 300-Blackout
| Hornady 6.5 Grendel 125-grain fmj | |||||
| Range | Drop | Windage | Time | Energy | Velocity |
| (yds) | (in) | (in) | (s) | (ft./lbs.) | (fps) |
| 0 | -1.50 | 0.03 | 0.00 | 1818 | 2580 |
| 100 | 0.00 | 0.91 | 0.12 | 1540 | 2375 |
| 200 | -4.69 | 3.66 | 0.25 | 1297 | 2179 |
| 300 | -16.73 | 8.54 | 0.40 | 1084 | 1992 |
| 400 | -37.56 | 15.84 | 0.56 | 901 | 1816 |
| 500 | -68.97 | 25.88 | 0.73 | 745 | 1651 |
| Hornady 300-Blackout 125-grain fmj | |||||
| Range | Drop | Windage | Time | Energy | Velocity |
| (yds) | (in) | (in) | (s) | (ft/lbs.) | (fps) |
| 0 | -1.50 | 0.04 | 0.00 | 1313 | 2175 |
| 100 | 0.00 | 1.98 | 0.15 | 968 | 1867 |
| 200 | -8.58 | 8.36 | 0.32 | 703 | 1591 |
| 300 | -31.01 | 20.12 | 0.53 | 509 | 1354 |
| 400 | -72.52 | 37.97 | 0.77 | 379 | 1168 |
The real issue with the 300-Blackout is its small case capacity. It just doesn’t have enough space in the case for a lot of powder. Some people say that the Blackout competes with the 7.62×39, but it really doesn’t. The Blackout is about 15 percent less powerful and has 50 percent more drop at 300-yards. Hardly in the same class.
The 6.5 Grendel is sleek, efficient, and slimline. It starts out with more energy than the Blackout, and it keeps its energy better so it takes longer for it to slow down. That makes for a cartridge that is flat shooting for a long way downrange.
Sure, there are a lot of different bullet designs and weights that play into things. But, by and large, the Grendel is much more capable for general hunting and shooting than the Blackout.
The Grendel really doesn’t have much variety in bullet weight. there used to be a 150-grain load, but almost everything is 123-grains now. the Blackout has standard bullet weights between 110 and 135-grains, and it has subsonic loads with bullets from 190 to 220-grains. Let’s look at a variety of common loads and their ballistics charts.
6.5 Grendel vs 300 Blackout Balistics Chart
These ballistic charts use a 100-yard zero.
| (drop/energy) | 50-yards | 100-yards | 200-yards | 300-yards |
| 300 Blackout 220-grain fmj | +3.76 in/984 fps | 0.0 in/970 fps | -35.4 in/943 fps | -109.9 in/919 fps |
| 300 Blackout: 110-Grain TTSX | +.24 in/2098 fps | 0.0 in/1952 fps | -7.7 /1680 fps | -27.8 in/1441 fps |
| 300 Blackout 150-grain Deer Season XP | +.5 in/1850 fps | 0.0 in/1801 fps | 9.2 in/1705 fps | -35.9 in/1230 fps |
| (drop/energy) | 200-yards | 300-yards | 400-yards | 500-yards |
| 6.5 Grendel 123-grain SST | 4.5 in/2180 fps | 16 in/1990 fps | 35 in\1811 fps | 64 in\1643 fps |
| 6.5 Grendel 123-grain fmj | 5 in/ 2197 fps | 17 in/1992 fps | 37 in/1861 fps | 69 in/69 in |
| 6.5 Grendel 123-grain ELD-M | 4.51 in/2244 fps | 15.94 in/2086 fps | 35 in/ 1935 fps | 64 in/1790 fps |
Ballistic Coefficient
The 6.5 Grendel averages a much higher Ballistic Coefficient than 300-Blackout, with the exception of heavy bullets intended for subsonic loads. The 300-Blackout subsonic has a higher Ballistic Coefficient, but they are so slow and heavy that they have a shorter effective range than the lighter bullets.
The Ballistic coefficient is the metric of how aerodynamic a bullet is. Generally, a higher Ballistic Coefficient is associated with a heavier bullet. There’s a lot more to it, but that’s the most obvious. A bullet with a higher Ballistic Coefficient will keep its kinetic energy better because it has a lot of energy and less wind resistance.
Here are the Ballistic Coefficients of the most popular bullets loaded for 300 Blackout.
| Supersonic 300-Blackout | Subsonic 300-Blackout |
| 110-grain CX, (all-copper bullet) BC .312 | 208-grain A-max BC .648 |
| 125-grain fmj BC .250 | 190-grain Sub-x BC .437 |
| 135-grain FTX BC .274 | |
| 125-grain hp-match BC .320 | |
| 110-grain V-max BC .290 | |
| The average BC of popular Supersonic bullets is .289 and the average weight is 121-grains | The average BC of poplar subsonic bullets is .542 and the average weight is 199-grains |
Now let’s look at the BC of common 6.5 Grendel bullets
| 6.5 Grendel |
| 123-grain ELD-M BC.506 |
| 123-grain fmj BC.420 |
| 123-grain SST BC. .510 |
| 100-grain fmj BC. 505 (WOLF/Barnaul) |
| The average BC of these bullets is .478 and the average weight is, well, 123-grains |
The higher average BC of the Grendel bullets makes a huge difference to both penetrations and to a flat trajectory. that’s what makes the Grendel capable of long-range shooting. Most bench rest shooters consider the Grendel a fine 750-yard gun, but a lot of shooters have stretched it past 1,000-yards.
The 6.5 Grendel is a great deer hunting cartridge to 300-400 yards. The Blackout is usually limited to 300-yards for target shooting, under 200-yards for hunting, and 100-yards for hunting with subsonic.
Ammo Price
Both are a bit expensive when it comes to ammo. Neither are all that common and they sort of fall into the realm of specialty cartridges. That’s only because they aren’t mainstream, but it does mean the ammo gets costly. Most ammo for both will run from 50-cents to a buck-fifty a bullet.
The Blackout tends to have ammo just a bit cheaper in stores near me. But really, neither are a cheap gun to feed with good ammo. Be prepared to either reload or pay up if you want to shoot a lot.
Wolf Ammo is a cheaper option for both, and it’s fairly popular. Wolf is an importer of European-made ammo. Most of the stuff they import is old-school steel-cased ammo. Their 6.5 Grendel is actually made by Baraul and it has their brownish-green lacquered case. Wolf 300-Blackout looks to be Tulammo, but I’m not 100% sure.
Wolf just takes others’ ammo and puts it in their own package for importing. It’s not super accurate stuff. It’s accurate enough for plinking. Shucks that ammo is accurate enough for general issue to most militaries in the world. It usually around shoots 3-4 MOA, which isn’t far from the US military standard ammo.
Right now, it’s about $20 for 20 rounds of Wolf 6.5 Grendel and $15 for 20 rounds for Wolf 300-Blackout. It works in most guns just fine, but if you have a rough chamber, the coating on the cases can hang up more than a brass case would.
Supressed
The 300-Blackout is much quieter with a suppressor than the 6.5 Grendel. The Blackout was tailor-made to work best with heavy, subsonic bullets and a suppressor. The subsonic ammo also functions very well in barrels as short as 10.5-inches, losing very little velocity.
That’s what the Blackout was made for. It was designed to cause good damage from a 10-inch barrel and be super quiet with a suppressor. The designer envisioned it for military tactical use in urban environments and close-quarters situations where you want a small, quiet gun.
Before the Blackout, the best options for short, quiet guns were really 9mm and 45acp compact carbines, but those didn’t have enough energy. The Blackout certainly outclasses those. It’s quiet, has little muzzle flash, and very little recoil.
Recoil
300 Blackout averages 4 pounds of recoil and 6.5 Grendel averages 6 pounds of recoil. The Blackout has 50 percent less recoil than a 6.5 Grendel but both are quite low-recoil options. Neither is too much for a small-shooter or recoil-sensitive people.
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