Shoot Like SOCOM: The 6.5 Creedmoor Cartridge & its Long Distance Relationship with CMMG’s Endeavor Mk3

In 2018, US Special Operations Command adopted the 6.5 Creedmoor (CM) as their new Precision Rifle cartridge. In May 2020, a specialized group from the U.S. Department of Defense has replaced their MK13 bolt-action 300 Winchester Magnums with a 20-inch semiautomatic AR-10 in 6.5 Creedmoor. With less recoil, 6.5CM provides enhanced accuracy and performance while reducing ammunition and rifle weight.

US Army sniper Photo courtesy of Defense Visual Information Distribution Service

Compared to the M118 Special Ball Long Range (.308 Winchester loaded with a 175gr Sierra Match King Boat-tail Hollow Point bullet) formerly used by special operations snipers, the 6.5 Creedmoor has 33% longer effective range with less recoil. At 1000 meters, it has double the hit probability, retains 30% more energy and has 40% less wind drift.

The long and the short of it, the 6.5 Creedmoor (left) will run in the same short action as the .308 Win. (center). 30-06 Springfield (right) requires a long action.

When USSOCOM picks a round, you can bet they have done their homework. When thousands of hunters and long-range shooters pick the same round, there is something interesting going on. I am slow to adopt new calibers, but 6.5 Creedmoor deserves the hype.

The 6.5 Creedmoor was developed for world-class performance. In 2008 Hornady’s senior ballistician and long-range shooter, Dave Emary sought out ideas from the long-range community for an improved 1,000-yard cartridge.

Emary modified a .30 Thompson Center (.30 TC) case to shoot .264″ bullets. The cartridge had a large case capacity optimized for use with 4350 class propellants paired with a rifle with a relatively fast 1:8″ rifling twist rate. The squat 1.92-inch case could accommodate long, heavy, high ballistic coefficient (BC) bullets in a short action magazine without intruding into the powder column.

To match shooters, the 6.5CM cartridge is a flat-shooting, light-recoiling target cartridge that offers the best balance of external and terminal ballistics and recoil that you can achieve from a short action rifle.

6.5mm bullets occupy a sweet spot in bullet diameter and offer the best of everything, USSOCOM didn’t buy the 6.5CM to punch holes in paper, even if that paper is small and very far away. If you put all that energy behind a well-designed bullet, it produces enough terminal ballistics to stop any mammal in North America. It will stop a terrorist anywhere on Earth. 

6.5CM has a high sectional density (SD). SD is the ratio of an object’s mass to its cross sectional area. Sectional density is important because it has a direct correlation to penetration. A high SD produces higher potential and exceptional terminal ballistics.

Ballistic coefficients (BC) is a numerical description of a bullet’s aerodynamic properties. High BC provides less drag against air resistance and wind drift. 6.5CM remains supersonic at 1,000 yards, still moving at 1,400 fps. This is important because accuracy drops dramatically when the bullet slows below the speed of sound.

If we compare a 165-grain .30 caliber bullet fired from a .300 Winchester Magnum and a 140-grain in 6.5CM (0.264 caliber) bullet, the BC of the two rounds is almost identical. This means that if the rounds are fired at the same velocity, they’ll both strike the target at the same time, with the same wind drift and drop. The .30 will require more energy to push the heavier bullet to the same velocity. That requires a larger cartridge case, a larger rifle, more weight and generates more recoil.

6.5 Creedmoor on the left, 300 Win Mag on the right.

The SD of a 165-grain 0.30-caliber bullet is 0.248. The 140-grain bullet in 6.5 mm (0.264 caliber) has an SD of 0.287. For a .30 caliber bullet to have the same SD as a 140-grain 6.5-caliber bullet, it would require a 190 grain bullet that would produce almost twice the recoil.

500 yards is a very long way. At the end of the road is a 3 x 2 foot white target. The 60X zoom on the Nikon Monarch spotting scope was able to see individual 6.5 caliber bullet holes.

With the military producing 6.5CM ammunition, the cost is coming down and availability is improving. That is important in an ever-changing environment. SIG SAUER ammunition has embraced 6.5 CM with a hunting load and a precision match load. SIG does their homework and doesn’t do anything halfway. SIG ammunition is made in Arkansas and is among the best in the industry.

300 Yards is no challenge for SIG’s Elite Hunter ammunition. The black squares are 1 inch wide.

6.5 Creedmoor, 130GR, Elite Hunter Tipped Concentric blackened jacket ensures reliable explosive expansion while delivering devastating on-game performance.

Elite Hunter Quick Specs

6.5 Creedmoor
130 gr
2850 fps
2344 ft-lb

This was my best 500-yard group of the day. My rifle really likes the Elite Hunter. There was light rain and some wind. I over corrected on the wind, but the group was so good I decided not to walk another 1000 yards to make an adjustment and re-shoot it. Judge the rifle, not the shooter.


– Exclusive jacket design delivers devastating on-game performance for medium to big game at extended ranges
– Concentric blackened jacket ensures reliable explosive expansion
– Translucent yellow tip increases ballistic coefficient, improves terminal performance, and aids in consistent reliable chambering- Enhanced boat tail design provides superior flight characteristics over a wide range of velocities
– Nickel-plated cases to aid in extraction while providing significant anti-corrosion qualities
– Custom formulated and precision loaded powders deliver consistent velocities regardless of atmospheric conditions
– Industry-leading primers are matched to proprietary powder blends to ensure dependable ignition

6.5 Creedmoor, 140GR, Elite Match Grade, OTM
When long-range accuracy is key, use our Elite Match Grade OTM ammunition to ensure the best shot possible.

Elite Match Grade Quick Specs

6.5 Creedmoor
140 gr
2690 fps
2249 ft-lbs

My 6.5CM rifle is an Endeavor 300 from CMMG. This AR-10 style design is built on receivers made of billet 7075 T6 aluminum powered by a rifle-length direct-impingement gas system.

CMMG Mk3 rifle with Nikon BLACK FX1000 6-24×50SF Long Range Rifle Scope and Warne Skyline Precision Bipod. SIG SAUER Elite Performance Ammunition 6.5 Creedmoor 140 gr OTM Match.

The Premium 24″ 416 stainless steel heavy taper profile barrel which favors heavier bullets. The muzzle is threaded 5/8-24 and capped by CMMG’s very effective SV muzzle brake. You can add a muzzle device or suppressor of your choice.

Mk3 comes standard with a Giessele SSA two-stage trigger, CMMG’s own 15-inch, free-float, 6061 T6 aluminum M-LOK handguard, a Magpul MOE pistol grip and PRS fully adjustable stock. It weighed in at 11.3 pounds before scope and bi-pod.

The Mk3 has a shell deflector but no forward assist. My rifle is finished in Titanium Cerakote with the safety lever, bolt catch, magazine release, charging handle, and muzzle brake in matte black. Controls are where you expect for an AR.

There is no forward assist, which cuts off a little weight. The bolt carrier and carrier key are chrome-lined. CMMG rifles have a lifetime warranty against defects in material or workmanship.

CMMG has seen the light offering three rifles in 6.5CM each appealing to a different price point. The Endeavor™ 200, Mk3 and Endeavor™ 100, Mk3 both with 20 inch barrels and different furniture.

Rifle, Endeavor™ 300, Mk3, 6.5 Creedmoor

Rifle, Endeavor™ 200, Mk3, 6.5 Creedmoor

Rifle, Endeavor™ 100, Mk3, 6.5 Creedmoor

The CMMG Mk3 is not too long to pack in with Slumberjack’s Deadfall 65 Pack. The Perception DST (Disruptive Shadow Technology) camouflage pattern makes an approach that much easier.

Endeavor 300, Mk3, 6.5 Creedmoor Quick Specifications

BARREL: 24” 1:8 Twist, 6.5 Creedmoor, Heavy Taper 416SS Barrel

MUZZLE: CMMG SV Brake, Threaded 5/8 – 24


FURNITURE: Magpul MOE Pistol Grip, Magpul PRS stock

RECEIVERS: Billet 7075-T6 AL

TRIGGER: Geissele SSA two-stage



The Geissele SSA two-stage trigger has a light initial take-up before meeting a solid stop. The trigger then breaks crisply with an average pull weight of around 4 pounds. This trigger combined with an 11-pound rifle in 6.5 CM is a joy to shoot. Felt recoil is similar to .223.

The Warne Skyline Precision Bipod provides a strong stable platform for your rifle. Designed to attach to your Picatinny rail, the Skyline allows you to make smooth one handed cant and panning adjustments on uneven terrain in less than ideal positions.

My scope for this project is Nikon’s BLACK FX1000 6-24×50SF. Engineered for both precision long-range rifle and action-shooting, it has great glass, first focal plane reticle, and return-to-zero integral zero-stop precision turrets. The FX1000 has all the quality features you want for long-range at half the price of competitive scopes.

I wanted to top this off with a great suppressor, I chose GSL’s GT-MAG suppressor. Originally designed for 300 WIN MAG, I knew it would be tough. The energy and pressure from 6.5 CM is no joke. I wanted a direct thread for this application for maximum repeatability.

GSL’s GT-MAG suppressor is now available in a dedicated 6.5mm Creedmoor model featuring a built-in suppressor retention system to keep the suppressor from backing off during operation.

The GT-MAG features a self-locking spring loaded suppressor retention system to keep the suppressor from backing off during operation. This is a big deal. There is nothing worse than a can that backs off and I have seen more than one suppressor fly down range. GSL’s GT-MAG suppressor was designed for 300 WIN MAG. Now available in a dedicated 6.5mm Creedmoor model, it features a built-in suppressor retention system to keep the suppressor from backing off during operation.

GT-MAG Quick Specs:

Caliber: 6.5mm Creemoor

Sound Reduction: 28 dB

Length: 8.8″

Diameter: 1.50″

Weight: 17.3 oz.

Materials: Titanium

Finish: High Temperature Cerakote

Mount: 5/8 – 24 Thread

MSRP: $985.00

Target Crown on Muzzle

Barrel Requirement: 18″ minimum length 6.5mm Creedmoor

CMMG Rifle, Mk3 with Nikon BLACK FX1000 6-24×50SF Long Range Rifle Scope and Warne Skyline Precision Bipod. SIG SAUER Elite Performance Ammunition 6.5 Creedmoor

Featured image: Shooting 500 yards at the Mountain View Range in Chehalis, WA with the CMMG Mk3 in 6.5 Creedmoor on a Warne Skyline Precision Bipod. The 60X zoom on the Nikon Monarch spotting scope was able to see individual 6.5 caliber bullet holes.

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About the author: Mark Miller is a former Customs Agent and a Green Beret who served in Afghanistan and a number of other live fire locations. A student of firearms and shooting, he is an FFL and a SOT. The guiding philosophy of his life is that terrain and situation dictate tactics and the enemy always gets a vote on any plan.

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  • Michael Lindley July 30, 2020, 7:10 pm

    For all the same reasons, I bought both of my daughters rifles in .260 Remington, a ballistic equivalent to the 6.5 Creedmoor (if not a touch faster).

  • Duke Wilson July 30, 2020, 2:44 pm

    I bought a 6.5cm in a savage arms Ar 10 platform.I used various makes of ammo. I put a 3×9 Leo scope on it . I shot this scope on many hunting rifles. I never got better than 1 inch groups at 75 yards on the AR .The shots keep climbing on me going north. So I assume the barrel is touching somewhere on me. So I gave it to a gunsmith friend of mine to try. He had the same results. I call and emailed Savage Arms and never heard back from them.I hunt with a sako 2506 with a 26″ shelin SSbarrel. I have dropped mule deer, elk in there tracks at 400 plus yards more than once.

  • Ben Dover July 27, 2020, 10:18 am

    I just bought a desert tech srs a2 covert in 6.5 creedmoor. Never shot the creedmoor before, I hope it’s worth the hype.

    • Flory July 28, 2020, 2:26 pm

      I just purchased a Savage 110 Tactical 6.5 Creedmoor. It’s got a 10 shot mag and it’s my first bolt action. Within my first 20 shots at 200 yards, I was already getting a 1.5 inch grouping on bullseye – and I have never shot bolt action or 6.5 in my life. I am super pleased and really happy with my choice.

  • Bob July 27, 2020, 9:00 am

    Sweet package. It’s a bit heavy for hunting – but that’s just me. I get the short, fat, Creedmoor thing. But I’m sticking to my .260 Rem for my hunting needs. It has worked well for many years. It should match the Creedmoor in downrange effectiveness. It’s just as fast out of the barrel and after that neither rifle or brass design has anything to do with bullet performance. If I were buying a new hunting rifle – yah, why not buy it in 6.5 Creedmoor – just to say I did. But I think it would be a step backward – albeit a small step. Again, nice package.

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