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The Windham Weaponry CDI (Carbine Diamondhead Integrated)

November 19, 2013
Bill Waugaman - Staff Writer , Ohio Valley Outdoors

Never having owned or ever shot an AR-platform rifle, I finally succumbed to the allure and decided to review a modern sporting rifle. The rifle chosen was built by one of the newest manufacturers in a highly competitive market, Windham Weaponry, located in Windham, Maine. Even though this young company just celebrated it's second anniversary, there is over two decades of experience that go into the manufacture of these rifles. You can read their inspiring story at: .

When reviewing and evaluating any firearm, knowing how it's built is important. Anyone reading this review familiar with AR-platform rifles will probably find it boring. Others considering the purchase of an AR-platform rifle for the first time should find this informative and will get insight for comparing other AR-platform rifles.

How Its Built

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* The Receiver is forged from 7075-T6 aircraft aluminum and given a black anodized, hard coat finish. The receiver has two parts, commonly referred to as the 'upper' and 'lower' receivers. The upper receiver is an M4A4 type flat top meaning it has a standard Picatinny rail for attaching accessories. The barrel assembly and bolt assembly are incorporated into the upper. The lower receiver contains the trigger assembly, trigger guard (aluminum, not plastic), safety, magazine release and bolt release. The stock and handgrip are attached to the lower.

The basic receiver design is no different from any of the other manufacturers, but that is what makes it special. While researching for this review, one person referred to the AR-platform as an 'erector set' rifle. You have the flexibility to change out parts like the receiver, stock, handgrip, trigger assembly, sights, magazines, hand guards, bolt, bolt carrier, and so on.

For quick access to the internal mechanisms, push out the takedown pin by the safety and the upper and lower pivot open. To separate the upper and lower, remove both the takedown and pivot pins. The quality of receiver halves fitting together is one of the first things the local FFL dealer inspected when the rifle arrived. He pointed out that the machining of the upper and lower mating surfaces and the tight tolerances of the takedown and pivot pins gave the CDI upper and lower a very good fit to each other.

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Windham Weaponry CDI

* The Barrel is a typical 16" carbine length with an M4 profile having a 1 in 9" RH twist. Windham Weaponry barrels are made from 4150 chrome moly vanadium 11595E steel (mil-spec). This steel has an increased carbon content to add strength and durability. The bore is chrome lined to prevent corrosion that extends barrel life and makes cleaning easier. The feed ramp at the back of the chamber is M4 mil-spec meaning that it is cut wider and lower to improve cartridge feeding under adverse conditions from the magazine into the chamber.

* The Bolt is made from Carpenter 158 steel and 8620 grade steel is used for bolt carrier, both of which meet mil-spec standards. Both the bolt and bolt carrier are phosphate-coated and chrome-lined. The bolt carrier has an M16 contour that is stronger and heavier than a commercial grade bolt to ensure longer and more reliable operation.

* The Trigger is a typical single action trigger found in AR-platform rifles. The trigger pull is about 8 pounds with a slight take-up. When the trigger is released after being fired, there is a 'click' as it resets, common for this type of rifle. While this is trigger would be suitable for plinking or some types of competitive shooting, having a better trigger would definitely help target shooting results.

* The Action is a semi-automatic, gas impingement system. Gas pressure created when a cartridge is fired is used to push the bolt assembly backward to eject the spent casing. This is accomplished through a gas port in the barrel, a gas block on the outside of the barrel and a metal tube running from the gas block to the bolt carrier. A gas impingement system is not the same as a blowback or gas piston designed semi-auto.

* The Safety on left side of receiver is easily controlled with your thumb; rotate clockwise for 'fire' and counterclockwise for 'safe'. Markings on both sides of the receiver indicate the safe/fire status.

* The Receiver Extension for attaching the stock is a commercial grade that has a slightly larger diameter than mil-spec. The CDI comes with an adjustable stock. If you want a fixed length stock or another style of adjustable stock, it's an easy switch.


While many shooters will start with a basic rifle and then upgrade with aftermarket enhancements, the CDI comes from the factory already equipped with six premium aftermarket enhancements. Who better than the manufacturer knows what accessories work best with their own firearm?

* Magpul MOE Carbine Stock This is a 6-position adjustable stock that mounts on a commercial spec carbine receiver extension tube. The sling loop will accommodate slings up to 1 " wide. The replaceable rubber butt-pad is over " thick. The maximum length of pull adjustment is 3.8". A premium chrome-silicon lock spring provides positive locking of the stock in the desired position. (MSRP $60)

* Magpul MOE Handgrip The handgrip is a one-piece reinforced polymer construction with a storage compartment inside the handle easily accessed from the bottom of the handle. The handgrip has a comfortable ergonomic shape that feels good and is complimented with an aggressive texturing for a secure grip even in less than desirable weather conditions. (MSRP $21)

* Magpul AFG Angled Foregrip Being angled, this foregrip fills the void between holding the handguard and holding a foregrip mounted perpendicular to the handguard. The angle allows for a natural and comfortable hold since the wrist does not have to be rotated. This will cut down on fatigue resulting in better control of the rifle. If you don't like the finger shelf, the Angled Foregrip comes a replaceable piece to make the grip surface smooth. (MSRP $35)

* Diamondhead Handguard The CDI is equipped with the Diamondhead VRS 10.25" Free-Floating Handguard made from anodized 6061 aluminum. This handguard extends the Picatinny rail on the flattop receiver to over 16" of continuous length. It is a free floating design with a proprietary clamping system for a rigid, secure attachment. Since this handguard does not contact the barrel, the rifle's accuracy is not affected. The design protects the gas tube and allows for airflow to keep barrel cooler for more consistent accuracy. The quad configuration allows for accessories to be attached on both sides and the bottom. The Diamondhead Handguard is covered by the Diamondhead exclusive Lifetime Warranty. (MSRP $159)

* Diamondhead Sight System This sight system consists of the Diamondhead front and rear sights. The Diamondhead front sight attaches to the Picatinny rail and features a proprietary diamond-shaped housing. The front sight post is adjustable for elevation and interchangeable with any standard A2 post. The Diamondhead rear sight is also a proprietary diamond-shaped aperture with reference posts and horizontal bars. This shape gives fast target acquisition and allows the eye to naturally center the target in the aperture. The rear aperture easily changes between a small or large aperture opening and is windage adjustable in .5 MOA increments. Since they both attach to the Picatinny rail, they're in the same sight plane. Both the Diamondhead are made with mil-spec stainless steel and black anodized 6061 T6 aluminum. Both sights flips up when needed, fold down with the push of a button, lock securely in place, and remain zeroed. These sights are covered by the Diamondhead exclusive Lifetime Warranty. (MSRP $238)

* Smith Enterprise Vortex Flash Suppressor This open-ended flash suppressor definitely looks different with its four-pronged, 15-degree right-hand helix twist. The Vortex is made from case hardened 8620 bar stock and a manufacturing process that adheres to very tight tolerances. The thread pitch on the Vortex is checked on both cold and hot barrels to insure a proper and secure fit at all times. The Vortex is machined so that it seats on the shoulder and muzzle at precisely the same point during rotation. These tight tolerances and the unique design increase the structural rigidity and ensure the suppressor will not come loose. Smith Enterprises makes the Vortex Flash Suppressor for the CDI since Windham Weaponry's barrels meets the strict tolerances required for proper fit and function. (MSRP $65)

The Windham Weaponry CDI comes from the factory with a foam lined, hard plastic gun case, a black web sling and an Ambidextrous Telestock Endplate that makes it possible to attach a variety of slings, including single point mount types. A Tapco chamber flag doubles as a tool for removing the takedown/pivot pins and a tool for adjusting windage/elevation on scopes. These included accessories are a $40-$50 savings over having to purchase them separately. The CDI comes with one magazine manufactured for Windham Weaponry to their specifications.

Accuracy At the Range

Range testing the CDI was done with two objectives, check for accuracy and check for reliability.

In conversations with people familiar with AR-platform rifles, it sounded like 1.5 to 2.5 moa accuracy with premium ammunition is typical with a 16" standard barrel, not heavy or target grade. The CDI far exceeded my expectations and everyone assisting with this review. This rifle shot as good as or better than some of the hunting rifles I have reviewed over the years.

To check accuracy, the CDI was equipped with a Leupold Mark AR MOD-1 Tactical Scope using a Mark 2 Intregral Mounting System. A Caldwell Lead Sled DFT was used to support the rifle. The results for ten 3-shot groups were as follows:

Black HillsRemanufactured55Soft Point0.51.20.9
Cor-BonUrban Response55JHP0.61.51.0
HornadyVarmint Express55V-Max0.91.61.3
WolfPolyformance (steel)55FMJ2.43.33.0

All ammunition produced very good results. The big surprise was Black Hills Remanufactured. It shot really well in the CDI. Cor-Bon Urban Response was a very close second. Federal Fusion was the most consistent. Hornady results were nearly identical with two different loads. While the Barnes and Winchester may not have been as accurate as the others, they still averaged less than 2 moa accuracy. Individuals assisting with the range testing commented that the Wolf Polyformance accuracy was equal to or better than what they had experienced in other rifles.

The best accuracy result for all of the ammunition tested was when the CDI was fired at a slow deliberate pace. As the barrel got hot from repetitive or faster paced shooting, the groups tended to open up.

As with any testing for accuracy, the variables that can and will affect results are many. A cartridge that performs well in one firearm does not mean it will have the same result in other firearms. The general point of impact can vary in the same rifle from different cartridges.

It's obvious that the Windham Weaponry CDI shot very respectable with all ammunition tested.

Reliability At the Range

Reliability testing consisted of using a variety of magazines loaded with Black Hills Remanufactured, Winchester Target and Wolf Polyformance. The CDI was fast fired in strings of 10 to 30 rounds, strings of 10 with magazine changes, double taps, paced firing and random speeds. More than a thousand rounds were fired over two days. There was not a single jam, failure to extract or failure to load attributed to the CDI.

Since magazines are a key factor in the functionality of any AR-platform rifle, testing of how well the CDI handled magazines from various manufacturers was part of the evaluation. Forty-six different magazines from 11 different manufacturers (Ammunition Storage Components, C Products Defense, Cammenga, D&H, E Lander, NHMTG, Magpul, ProMag, Tapco, Thermold, the Windham Weaponry magazine, and 30 year old Army issue magazines) were tested in the CDI. The magazines were polymer, aluminum or steel construction, and had capacities ranging from 5 to 42 rounds.

In total, over 2,300 rounds were shot from the CDI to test accuracy, reliability, retesting and just some plinking fun. This rifle functioned flawlessly regardless of the magazines, ammunition, weather conditions or whether the barrel and action were hot or cold.

Final Thoughts

Before starting this review, becoming familiar with AR-platform rifles was a necessity. I relied on some very knowledgeable friends, the local FFL dealer and internet research. It is very obvious that most AR-platform rifle enthusiasts are very opinionated and very biased, akin to the never-ending Ford vs. Chevy battle. Without having any preconceived notions, this evaluation was done from an unbiased perspective.

The quality and craftsmanship of the Windham Weaponry CDI is very good. The MSRP of $1680 seems on the high side, but when $578 of aftermarket enhancements and $40-$50 of additional accessories are taken into consideration, the retail price is very competitive. Windham Weaponry does offer 11 other models of AR-platform rifles with an MSRP starting at $958.

Accuracy and reliability definitely exceeded expectations. With the right cartridge, the CDI is capable of accuracy as good as many bolt action rifles making it very suitable for hunting or target shooting. Good reliability gives the CDI a definite advantage for combat style or competitive shooting. While the factory trigger is typical of AR-platform rifles, a better functioning trigger could improve any shooter's ability with this rifle. That's the beauty of an AR-platform riflethe ability to easily change out parts like the trigger assembly.

Even the Operating and Safety Manual is an indication of Windham Weaponry's attention to quality and detail. It is printed in full color and is very detailed.

The warranty on all Windham Weaponry rifles, including the CDI, has to be one of the best in the industry. It is a lifetime warranty on the rifle covering defects in material and workmanship. What sets this warranty apart is the fact that it is transferable to a subsequent owner of the firearm. Windham Weaponry is setting the bar pretty high for themselves, and the competition, with this warranty. From what I found with the CDI, they have achieved their goal.

A detailed review of the Leupold Mark AR MOD-1 Tactical Scope, Caldwell Lead Sled DFT and AR-Platform Magazines...How They Stack Up are available at



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