Bigger ARs: 6.5 Creedmoor, 6.5 Grendel, & 308 Winchester

The Core30 TAC II in 6.5 Creedmoor could be a 3Gun winner. The Alexander Arms Overwatch rifle in 6.5 Grendel might be your next deer rifle. But HKs MR762A1 was the bully on the block.


The history of popular firearms in the 21st Century (so far) has been indelibly marked by the rise of civilian-owned AR-15 semi-automatic rifles. What most people don’t know is that the system was originally intended to fire larger-caliber ammunition than 5.56mm or 223 Remington. Designed by Eugene Stoner, the AR-10 (the “AR” is short for “ArmaLite Rifle,” not “assault rifle” as many non-gunners believe) evolved from the 7.62x51mm NATO chambering to smaller calibers for greater reliability and practicality; in particular, soldiers were able to carry more ammunition because the bullets and magazines were smaller and weighed less. The structure of the rifle itself could be made lighter as well without the fear of receivers cracking or pins working loose. In this last regard, such was the state of metallurgy and machining in the 1960s.

Alexander Arms Overwatch rifle

Core30 TAC II rifle

AR-15 bolt carriers

In today’s manufacturing world, advanced technology provides for more exacting tolerances so that finished products are more consistent. And thanks to the space program and other factors, stainless steel and other metals are more malleable and durable than ever. With the Pentagon still chasing a more effective round than 5.56/223 and the public’s thirst for a bigger bang, a return to larger calibers for the AR platform was inevitable. In this test we compare three different ways to project larger-diameter bullets. Our first test rifle (or carbine, if you will) was the $3999 MR762A1 from Heckler & Koch. As its nomenclature suggests, the MR762 fires 7.62x51mm ammunition or its American incarnation, 308 Winchester. From Core15 rifles in Ocala, Florida, we chose the $2470 Core30 Tac II chambered in 6.5 Creedmoor, which fired 0.264-inch-diameter bullets. Our third rifle also shot 0.264-inch bullets, but from a cartridge case short enough to be housed in the smaller AR-15 chassis. Alexander Arms managed to stuff Bill Alexander’s invention, the 6.5 Grendel, into an AR-15 receiver and topped it off with a 24-inch-long barrel. List price of the Alexander Arms Overwatch rifle we tested was $1613.

Overwatch bag from

Overwatch bag from

For 6.5 Grendel shots of record, we chose 120-grain American Eagle, 123-grain Hornady A-Max, and Alexander Arms’ own brand of ammunition topped with the 123-grain Lapua Scenar bullet. Our H&K MR762A1 was treated to 110-grain FB-tipped rounds from Noveske, 168-grain OTM rounds, and 150-grain HT rounds from SIG Sauer, plus a diet of Black Hills Gold 155-grain Tipped Match King ammunition. The Core30 rifle was loaded with all Hornady brand ammunition; the 129-grain White Tail Interlock, 140-grain ELD Match, 143-grain Precision Hunter ELD-X, and 147-grain ELD-Match rounds.

Overwatch bag from

For optics we used both a 4-16x50mm Steiner Predator Xtreme scope and SIG Sauer’s new Tango6 4-24x50mm scope. The Tango6 is a compact scope for its maximum power of 24x magnification. In our view, this makes it a good choice for semi-automatic rifles that already have a lot of mass top to bottom thanks to the pistol grip, and you don’t want the rings or mount to put weight on the handguard. Both the Steiner and the SIG were first-focal-plane scopes so we could manipulate the size of the reticle. We especially liked using the small dot in the center of the Tango6 reticle. Not really visible until reaching 8x magnification, we were able to enlarge the dot to just the right diameter to indicate dead center but not significantly block the target.

308 Winchester Range Data

SIG Sauer 308 Win. 168-gr. OTM Heckler & Koch MK762
Average velocity 2519 fps
Muzzle energy 2367 ft.-lbs.
Average group 1.1 in.
Black Hills Gold 308 Win. 155-gr. TMK
Average velocity 2530 fps
Muzzle energy 2203 ft.-lbs.
Average group 0.8 in.
SIG Sauer 308 Win. 150-gr. HT
Average velocity 2683 fps
Muzzle energy 2397 ft.-lbs.
Average group 1.2 in.
Noveske 308 Win. 110-gr. FB Tipped
Average velocity 2933 fps
Muzzle energy 2101 ft.-lbs.
Average group 1.4 in.
To collect accuracy data, we fired five-shot groups from the prone position. Distance: 100 yards. We recorded velocities using a LabRadar Doppler chronograph.

6.5 Grendel & 6.5 Creedmoor Range Data

Alexander Arms 6.5 Grendel 123-gr. Lapua Scenar Alexander Arms Overwatch
Average velocity 2612 fps
Muzzle energy 1863 ft.-lbs.
Average group 0.6 in.
American Eagle 6.5 Grendel 120-gr. Open Tip Match AE65GDL1
Average velocity 2676 fps
Muzzle energy 1908 ft.-lbs.
Average group 0.7 in.
Hornady 6.5 Grendel 123-gr. A-Max 8150
Average velocity 2615 fps
Muzzle energy 1867 ft.-lbs.
Average group 0.7 in.
Hornady 6.5 Creedmoor Match 147-gr. ELD
Average velocity 2616 fps
Muzzle energy 2233 ft.-lbs.
Average group 0.9 in.
Hornady 6.5 Creedmoor Precision Hunter 143-gr. ELD-X
Average velocity 2586 fps
Muzzle energy 2123 ft.-lbs.
Average group 0.8 in.
Hornady 6.5 Creedmoor Match 140-gr. ELD
Average velocity 2649 fps
Muzzle energy 2181 ft.-lbs.
Average group 0.5 in.
Hornady 6.5 Creedmoor White Tail 129-gr. InterLock
Average velocity 2750 fps
Muzzle energy 2166 ft.-lbs.
Average group 1.1 in.
To collect accuracy data, we fired five-shot groups from the prone position. Distance: 100 yards. We recorded velocities using a LabRadar Doppler chronograph.

big bullets for AR-15 rifles

Tests were performed at American Shooting Centers in Houston, Texas. Accuracy data was collected from the 100-yard benches. We also made use of the 400-yard range where a variety of steel targets stood to challenge those who dare. We fired at the 18-inch-wide by 30-inch-tall IPSC/USPSA target to test our skills. With three rifles that were different in concept and caliber, we wondered if one would stand above the others in all aspects of performance. Or would each rifle claim supremacy when viewed in a specific role. Let’s find out:

Alexander Arms Overwatch 6.5 Grendel, $1613


Balanced, accurate, and well made, the Overwatch is more portable than any AR-10 and more powerful than smaller-caliber AR-15s. It is an excellent Modern Sporting Rifle.

Alexander Arms Overwatch 6.5 Grendel

ACTION TYPE Semi-auto, direct impingement
OVERALL LENGTH (min/max) 40.85 to 44 in.
BARREL 24 in.; 1:9 in. twist; Duracoat finish
OVERALL HEIGHT (w/o scope) 7.1 in.
WEIGHT LOADED (6+1, 140-gr.) 9.7 lbs.
ACTION FINISH Anodized aluminum alloy
MAGAZINE TYPE Detachable box, staggered
STOCK 6 position adjustable
LENGTH OF PULL (min/max) 10.5 to 14 in.
BUTTPLATE Rubber/polymer
SAFETY Rotating 2 position
WARRANTY None written
TELEPHONE (540) 443-9250

Alexander Arms Overwatch 6.5 Grendel

When it comes to getting more power out of the AR-15 frame, we think the 6.5 Grendel may be the last stop before moving up to a larger, heavier semi-automatic rifle. Indeed, complete upper assemblies chambered for 6.5 Grendel will fit on a standard AR-15 lower. But a dedicated 6.5 Grendel magazine, which resembles a 6.8 SPC magazine, must be used. Alexander Arms does offer an $882 complete upper, but we chose instead to test the complete rifle. Starting at a base price of $1312.50, we added a 24-inch long Shilen barrel (a $242 upgrade) and a 2.0-inch-diameter free-floated handguard constructed of composite G10 ($100). Similar to carbon fiber in appearance but not quite as lightweight (or as costly), the G10 not only kept weight down but it never seemed to heat up, no matter how many rounds we fired. The handguard offered two standard sling studs up front, supposedly one for a sling swivel and another for attaching a Harris-style bipod. Oddly, the five-position adjustable buttstock did not have a matching sling stud, but it did offer anti-rotational QD (quick detachable) swivel mounts available from either side. We solved this problem by attaching a $24 Grovtec GTSW-235 Base-to-Stud Adaptor up front so we could use the latest tactical slings that rely on push-button QD swivels. Grovtec also makes a $21 adapter to change a standard sling stud into a quick-detachable style (GTSW-299). Unlike our other test rifles, the Overwatch Rifle was small enough to be carried in a stealth backpack from Hazard4 Tactical, coincidentally also named the Overwatch.

Alexander Arms Overwatch 6.5 Grendel

The 24-inch-long barrel, finished with black Duracoat, telescoped in diameter from 0.9 inches beneath the gas block, which was exposed just beyond the end of the handguard, to a diameter of 0.70 inches before mating with a standard flash hider and crush washer. The opposite end of the Overwatch rifle was fit with a Primary Systems B5 SOPMOD BRAVO collapsible stock. SOPMOD stands for Special Operations Peculiar Modifications and refers to the concept of being able to configure the rifle to individual preferences and mission requirements. This was a $58 option. The solid cheekpiece offered a wide tri-oval profile similar to those stocks meant to stow batteries parallel to the buffer-spring tube, but no such capacity was available. Otherwise, the buttstock pad was compact, measuring just 4.9 inches top to bottom. The pad itself was rubberized and snapped on and off, held in place by one lug at the comb and pinch tabs toward the heel. In some cases, a catchy rubber pad is undesirable, thus the ability to remove it. The pad wobbled around a little bit, but that didn’t seem to effect our shooting. The buttstock, as a unit, did have some movement fore and aft but did not wobble side to side.

Alexander Arms Overwatch 6.5 Grendel

Top-end to lower fit was precise, and we were impressed with the overall construction of the Overwatch. The upper receiver featured a Picatinny rail. All pins, levers, and springs in the lower were clean and tight, adding up to a precise unit. The anodized finish was satiny and pleasing to the touch. Three additional trigger upgrades were available, including the $200 Geiselle SSA trigger, plus two Alexander Arms products named the Tactical Blade ($214) and the $203 Tactical Bow trigger. Nevertheless, our standard trigger broke cleanly and consistently at 5.5 pounds. Additional options included an MK10 handguard, six different muzzle devices, four additional choices of buttstock, and no less than 20 different surface coats. Set at a cost of $330, choices of finish included carbon fiber, typical military colors such as OD Green and FDE, plus a variety of Krypteks, foliage, and even a pattern of skulls.

At the range, we found that 6.5 Grendel in what is essentially a 5.56 platform provided noticeably more rearward poke to the shoulder. Not by any means as heavy as a 30-caliber AR-10, but it was a little bit of a surprise if by appearances the shooter thought he was about to fire a 223/5.56 AR-15. Recoiling directly rearward, the rifle gave little sense of torquing away from the shooter.

Feeding from the supplied 10-round magazine was reliable, and the magazine was easy to load. Additional magazines ranging in capacity from four rounds to 24 rounds were available from Alexander Arms for not more than $21. A heavily padded soft-sided carrying case was supplied.

Fired offhand, we found the Overwatch was very well balanced. The round handguard made for a very comfortable hold, and its generous 2.0-inch-diameter added stability. From the bench, all three test rounds broke the 1-minute-of-angle barrier with room to spare. According to our calculators, the 120-grain American Eagle Open Tipped Match rounds and the Hornady 123-grain A-Max ammunition each produced five-shot groups that averaged 0.70 inches across, within a couple of decimal points.

Given that Alexander Arms is the 6.5 Grendel expert, we weren’t surprised that the company’s proprietary ammunition featuring Lapua’s 123-grain Scenar bullet proved to be the most accurate, producing 0.60-inch-wide groups on average. We were able to guess our come-ups at the 400-yard range, and in fewer than 10 rounds, we were hitting the steel target.

Our Team Said: The quality of the build and accuracy were first rate. Even with upgrades attached, we think the Overwatch was a bargain and so were the extra magazines. We liked having the additional power of the 6.5 Grendel without adding any weight to the AR-15 design. We think the 6.5 Grendel Overwatch is a much more suitable tool for larger game than a 5.56/223 rifle. The Overwatch wasn’t necessarily larger than a bolt-action hunting rifle, and it’s much easier to tote than an AR-10.

Core30 TAC II Rifle 14898 6.5 Creedmoor, $2470


An upgrade in power for the precision 3Gun competitor, the Core30 is a first-class match rifle. Commercial chamberings are currently limited, so consider that in your buying decision.

Core30 TAC II Rifle 14898 6.5 Creedmoor

ACTION TYPE Semi-auto, direct impingement
OVERALL LENGTH (min/max) 39.9 to 43.20 in.
BARREL 20 in., 1:8 in. twist
OVERALL HEIGHT (w/o scope) 7.5 in.
WEIGHT LOADED (20+1, 147-gr.) 10.4 lbs.
ACTION Anodized aluminum alloy
BARREL Fluted black-nitrided steel; Core30 muzzle brake
MAGAZINE 20-rd. detachable box, staggered
BUTTSTOCK MagPul ACS, 6-pos. adjustable
LENGTH OF PULL (min/max) 12.5 to 15.8 in.
SAFETY Rotating 2 -pos.
TELEPHONE (352) 401-9070

Core30 TAC II Rifle 14898 6.5 Creedmoor

Core Rifle Systems is a division of Good Times Outdoors located in Ocala, Florida. The makers of the Core30 and Core15 rifles provide superior machining, whether it’s making custom airboats, knives, or firearms. Save for the CMC trigger, Magpul ACS six-position stock and MOE grip, Core rifles are fabricated and assembled completely in house. Some of the features include a 20-inch black-nitride barrel, muzzle brake, billet charging handle, forged upper and lower, aluminum handguard, low-profile gas block, chrome-lined 8620-steel bolt carrier, Magnetic Particle Inspected Mil-Spec 158 Carpenter steel bolt, chrome-lined gas key hardened to USGI specs, Grade 8 hardened fasteners, tool steel extractor and springs. All Core rifles are backed by a lifetime warranty.

Core30 TAC II Rifle 14898 6.5 Creedmoor

Core Rifle Systems sponsors a 3Gun shooting team, and our TAC II rifle was a good example of what they take to matches, such as those broadcast on the weekly television series 3Gun Nation. In terms of its martial capabilities, the CMC 3.5 trigger (which weighed in at about 3.25 pounds of resistance) may be too light for police work in our litigious world, but the four-pronged muzzle brake could most certainly double as an impact weapon. Law enforcement and military operators might rather choose from the list of about 40 other Core15 models built on the AR-15 frame (dubbed Core15) or from the Core30 AR-10-type rifles chambered for 308 Winchester and 6.5 Creedmoor.

The muzzle brake offered two large side-through ports and several round holes above. The aforementioned prongs helped break up muzzle flash. The stainless-steel barrel was sandblasted, but its shiny finish was revealed thanks to six lines of fluting that ran parallel to the bore. The handguard was skeletonized, offering keymod reliefs at 3, 6, and 9 o’clock. The 15.5-inch-long handguard was topped with a Picatinny rail offering 55 slots numbered 2 to 54. Four large bolts held the handguard in place.

Core30 TAC II Rifle 14898 6.5 Creedmoor

The upper and lower receivers were forged aluminum. The edges of the magazine well were flared. The front portion of the well was raised about 1 inch for faster reloads. There was no forward assist, and the ejection-port cover was etched on both sides with a boar’s head logo and the word Creedmoor, so it was visible whether the cover was open or closed. The integrated trigger guard was enlarged in an egg shape. The trigger itself was of straight profile, or actually an “L” shape with a measured length of 1 inch.

The MagPul ACS stock had a SOPMOD profiled comb, meaning the cheek piece was extended to either side with a rounded “A-frame” type profile. These extra contours were actually storage for cleaning tools or would be an exact fit for the 123 size batteries that are commonly used to power weapon lights. There was also additional storage in a compartment directly in front of the buttpad. It contained extra stock hardware and a solid-polymer 223 cartridge. The ArmaLite Rifle or AR-15/AR-10 can be field stripped and the front sight adjusted by using the tip of the bullet as a tool. But in this case, there was no front sight, and the trigger and hammer pins were threaded and capped to prevent rotation. So the detail of having a handy “cartridge” to perform these duties was ceremonial unless you add your own sights.

Core30 TAC II Rifle 14898 6.5 Creedmoor

We liked how the buttstock adjustment was lockable via a clamping lever that blended in with the lower structure. However, a quick-detachable sling swivel was out of the question because only a slot was provided for sling attachment. The base of the MagPul grip was capped, so its interior could also be used for storage as well. One 20-round MagPul PMag magazine was supplied.

HK MR762A1

From the bench, all but one of our rounds printed groups measuring less than 1 inch across. The 129-grain White Tail Interlock rounds performed well, but not by today’s 6.5 Creedmoor standards. But our tightest group measured just 0.35 inches across when the Core30 was loaded with Hornady’s 140-grain ELD Match ammunition. The average group size per five shots of this round measured about 0.5 inches across, or a half-MOA. With the SIG Sauer Tango6 scope in place, ringing steel at 400 yards could be achieved by changing elevation settings or simply by aiming with the reticle held a couple of notches above center.

Our Team Said: The trigger was light but not necessarily crisp. Instead, it had a progressive feel that was easy to engage. Fired offhand, the Core30 was well balanced and about as light as a 20-inch-barreled AR-10 rifle can be. The muzzle brake killed muzzle flip but was also very loud, making the gun tiring to shoot. The adjustable stock was solid, and the rifle was fast to reload, thanks to aforementioned sculpting of the magazine well. The average user may prefer a simple flash hider, but in the meantime, the Core30 6.5 Creedmoor should score big at the practical shooting matches.

Heckler & Koch MR762A1 7.62x51mm, $3999


Price and availability were the major drawbacks, but this rifle was powerful, well made, and fun to shoot.

Heckler & Koch MR762A1 7.62x51mm

ACTION TYPE Semi-auto, piston drive
OVERALL LENGTH (min/max) 35.6 to 39 in.
BARREL 16.5 in.; 1:11 in. twist, carbon nitride-coated steel
OVERALL HEIGHT (w/o scope or sights) 7.8 in.
WEIGHT LOADED (20+1, 168-gr.) 11.1 lbs.
SIGHT RADIUS 16.14 in.
ACTION Anodized aluminum alloy
MAGAZINE CAPACITY Detachable box staggered, 10 or 20 rds.
BUTTSTOCK 5-position adjustable
LENGTH OF PULL (min/max) 12.5 to 15.5 in.
SAFETY Rotating 2-pos.
WARRANTY Lifetime, original owner or designee at purchase
TELEPHONE (706) 568-1906

Heckler & Koch MR762A1 7.62x51mm

The HK MR762A1 has been referred to as the civilian version of the HK417 A2 battle rifle. The MR762A1 is assembled in the United States using American- and German-made components. Aside from available finishes and colors, plus some special fixtures, the primary difference, according to HK-USA of Columbus, Georgia, is that the military rifle utilizes a chrome-lined barrel. And that was more out of necessity than a desire for better accuracy since military rifles see harsher climates and are abused in ways that even law enforcement is unlikely to subject it to. So, in a time when the term Mil Spec is thrown about liberally, the construction of the MR762A1 includes several proprietary designs that exceed those specifications.

Heckler & Koch MR762A1 7.62x51mm

If you don’t read the owner’s manual, you might start out by voiding the warranty while attempting to split the upper and lower receivers. The takedown pins were held by a spring-loaded detent, for which a tool is provided. The takedown tool was stowed behind the rifle’s sizeable rubber-lined buttpad. To access the takedown tool, we rotated the buttpad counter-clockwise to open the storage chamber. Pressing in on the center of the takedown pin (and the same for the hinge pin) was required to free the pin and push it all the way out. If either pin were somehow left halfway out, it would stay in place and keep the rifle together. Bringing the locking pin back through the receiver also required the takedown tool. If lost, a small punch or a 5⁄64-inch Allen wrench will suffice. But the takedown tool works best because it automatically centers the tip.

Heckler & Koch MR762A1 7.62x51mm

Upon removing the bolt carrier, you might think you are in the land of giants. The bolt-carrier group alone is much bigger than that on an AR-15. The MR762 runs via a proprietary gas-piston operating system employing a solid operating rod. Like its military counterpart (the HK417), the MR762A1 was fit with a proprietary rail referred to as the FFRS or, Free Floating Rail System. This system was retained by two large bolts that were designed to stay in place by way of spring-loaded retaining screws found on the opposite side. In past runs, the handguard was configured as a “four-quadrant” rail with attachment spots at 12, 3, 6, and 9 o’clock. This MR762A1 was fit with an octagonal-shaped 2.05-inch-wide, 13.5-inch-long rail with keymod slots on each of the seven remaining sides. Extra-heavy-duty quick-detach sling lugs were embedded into the 10 o’clock and 2 o’clock positions nearest the handguard’s rearmost edge. The handguard was indexed and braced in part by a male lug that intersected with the rail atop the upper receiver located between slots numbered 18 and 22. In all, 58 slots were supplied.

Heckler & Koch MR762A1 7.62x51mm

The forged aluminum upper receiver offered a forward assist and a shell deflector. On the left-hand side, a guard was in place so that access to the bolt release was blocked from above and from a forward angle. The two-position safety levers were ambidextrous. The five-position adjustable-length buttstock offered three loops through which a sling could be attached—parallel and directly beneath the comb, plus two more loops located at 10 o’clock and 2 o’clock at the rear of the stock. The adjustment release was flush with the lower contour that swept downward diagonally from the center. Beneath the buttstock, the buffer tube held a short, proprietary buffer. Two magazines, one holding 10 rounds and the other 20 rounds, were supplied The magazines were a transparent gray plastic so the operator can keep track of ammunition supply. Magazines could be disassembled much the same as pistol magazines, by removing the basepad, spring, and follower. Regular cleaning and light lubrication was recommended. A military-quality soft carrying case was supplied.

After firing the Core30 TAC II rifle, the HK’s trigger caught some members of the test team off guard. Some shooters didn’t care for it at all, but others felt that the 6+ pounds of resistance was predictable and progressive.

Meanwhile, our wide choice of test ammunition allowed us to find out what the HK liked and what it didn’t. We had trouble consistently cycling the rifle with the Noveske 110-grain rounds, and accuracy averaged in the range of 1.4 inches per five-shot group. But all of our other rounds cycled happily in the HK. The SIG Sauer 168-grain OTM rounds and SIG Sauer 150-grain HT rounds landed average groups measuring about 1.1 to 1.2 inches across. Our best choice was the Black Hills Gold ammunition, with all groups measuring just less than 0.8 inches center to center.

The above groups were achieved with the SIG Sauer Tango6 scope in place. But when we arrived at the 400 yard range we hadn’t yet remounted the scope, so we decided to fire our 150-grain rounds at the steel targets using the supplied Troy Battle Sights raised from their folded “backup” position. We chose to fire at the steel IPSC/USPSA torso target that measured about 18 inches wide by 30 inches tall. Without changing the factory settings, we leveled the top of the front sight with the uppermost edge of the target. By now we were familiar with the trigger, and our test shooter hit the target in the upper chest area with eight consecutive shots.

Our Team Said: For anyone who has developed a “ho-hum” attitude toward the AR-15, the MR762 will be a very refreshing experience. One of our guest testers said it was as exciting as the first time they shot a 12-gauge shotgun. Even if it didn’t print tiny groups, it was certainly capable of sub-MOA accuracy, and we’re pretty sure this is the closest most people will get to firing a true military rifle that rings of precision and power. Availability of this rifle is limited and it is expensive, but it does give you the feeling this is the only self-defense rifle you’ll ever need.

Alexander Arms Overwatch

Core30 TAC II Rifle

Heckler & Koch MR762A1 7.62x51mm

Written and photographed by Roger Eckstine, using evaluations from Gun Tests team testers.


Please enter your comment!
Please enter your name here