6.5 Grendel vs 308 compares a light AR15 cartridge with the classic full-power short-action cartridge. The 308 Winchester fires heavier .308-inch bullets with roughly half again the energy, and it runs heavy subsonic loads. The 6.5 Grendel carries less energy but does it from a lighter rifle with much less recoil, and its slender 6.5mm bullets keep up with the 308 in wind. Chattahoochee Munitions manufactures firearms in both cartridges: the CM15 and CM7S in 6.5 Grendel, and the CM10 and CM7S in 308 Winchester.
6.5 Grendel vs 308 at a Glance
| 6.5 Grendel | 308 Winchester | |
|---|---|---|
| Bullet diameter | .264 inch | .308 inch |
| Case head | .441 inch | .473 inch |
| Maximum cartridge length | 2.260 inches | 2.810 inches |
| Typical supersonic bullets | 90 to 130 gr | 150 to 180 gr |
| Subsonic use | Not customary; bullets are too light | Yes, with heavy bullets and a 1:5 twist |
| Semi-auto platform | AR15 (CM15) | AR10 (CM10) |
| Bolt action | CM7S, Grendel bolt face | CM7S, .308 bolt face |
6.5 Grendel dimensions are from the SAAMI 6.5 Grendel cartridge and chamber drawing.
6.5 Grendel vs 308 Ballistics
The table compares a 123 gr 6.5 Grendel match bullet at Hornady’s published 2,580 fps with a 168 gr 308 Winchester match bullet at Hornady’s published 2,700 fps, both from 24-inch test barrels. Chattahoochee Munitions calculated the figures with a point-mass solver: 100-yard zero, 2.5-inch sight height, sea-level standard atmosphere, 10 mph full-value crosswind.
| Range | 6.5 Grendel 123 gr | 308 Win 168 gr |
|---|---|---|
| Muzzle energy | 1,818 ft-lb | 2,719 ft-lb |
| 300 yd energy | 1,180 ft-lb | 1,805 ft-lb |
| 500 yd energy | 863 ft-lb | 1,344 ft-lb |
| 300 yd drop | 14.0 in | 12.2 in |
| 500 yd drop | 60.4 in | 53.3 in |
| 500 yd wind drift | 23.1 in | 22.0 in |
The 308 carries about 50 percent more energy at every range. Drop is a few inches less for the 308 at 500 yards, and wind drift is almost the same, because the 6.5mm bullet is aerodynamically efficient for its weight. For full Grendel trajectory tables, read 6.5 Grendel ballistics.
Recoil, Weight and Rifle Size
The 6.5 Grendel vs 308 gap in recoil is large. The 308 launches a heavier bullet with a bigger powder charge, and it needs an AR10 or a short-action bolt action. The Grendel runs in an AR15: the CM15 6.5 Grendel weighs 6 lb 6 oz with a 16-inch barrel and 7 lb 4 oz with a 20-inch barrel, each with an unloaded magazine. Less recoil means faster follow-up shots and easier practice, which matters more than paper energy for many hunters.
Subsonic: Where the 308 Has a Role the Grendel Does Not
6.5 Grendel is a supersonic cartridge. Its bullets are too light to carry useful energy below the speed of sound, so it is not customarily loaded subsonic. The 308 Winchester can be: Chattahoochee Munitions loads a 300 gr Maker REX expanding subsonic, which needs a 1:5 twist barrel. If quiet, suppressed short-barrel shooting is the goal, see 308 Winchester subsonic and District 308. If the goal is a light, supersonic hunting rifle with mild recoil, the 6.5 Grendel fits.
6.5 Grendel vs 308 for Hunting
For deer, hogs and coyotes inside about 300 yards, the 6.5 Grendel with the right bullet does the job in a lighter rifle. For elk, large hogs at distance or heavy-bodied game, the 308’s heavier bullets give more margin. See 6.5 Grendel for deer and 6.5 Grendel for coyotes and hogs.
Suppressors
Both cartridges are supersonic with standard hunting loads. Chattahoochee Munitions recommends a flow-through suppressor on the gas-operated CM15 and CM10 with supersonic ammunition, and an enclosed suppressor on the manually operated CM7S bolt action. See 6.5 Grendel suppressor.
Chattahoochee Munitions 6.5 Grendel Firearms
- CM15 6.5 Grendel hunting rifle, 18-inch
- CM15 6.5 Grendel DMR, 18-inch
- CM7S 6.5 Grendel SBR, 12.5-inch
CM15 Grendel rifles use 416R stainless barrels with E100 Blackout Cerakote and a TriggerTech AR15 Duty trigger. See every model in Grendel’s Lair.
6.5 Grendel vs 308 FAQ
Is 6.5 Grendel as good as 308 for deer?
Inside about 300 yards, with a 120 to 130 gr hunting bullet, the 6.5 Grendel is an effective deer cartridge. The 308 carries more energy and gives more margin at longer range.
Does 6.5 Grendel have less recoil than 308?
Yes. It fires lighter bullets with a smaller powder charge, from a lighter AR15-size rifle.
Can 6.5 Grendel be shot subsonic like 308?
Not customarily. 6.5 Grendel bullet weights are too low for useful subsonic energy. The 308 Winchester runs heavy subsonic bullets such as the 300 gr Maker REX.
Which drifts less in the wind, 6.5 Grendel or 308?
In calculations with published match loads, they are within about an inch of each other at 500 yards in a 10 mph crosswind.
Is 6.5 Grendel vs 308 an AR15 vs AR10 decision?
Yes. In 6.5 Grendel vs 308, the Grendel runs in an AR15 and the 308 needs an AR10 for a semi-auto.
Who makes 6.5 Grendel and 308 rifles?
Chattahoochee Munitions manufactures the CM15 AR15 and CM7S bolt action in 6.5 Grendel, and the CM10 AR10 and CM7S bolt action in 308 Winchester.