Yankee Hill Machine’s Black Diamond Specter XL utilizes a lightweight skeletonized rail system, giving the carbine superior balance while minimizing the burden on operators in the field.

While there are many AR’s on the market that can be modified for patrol use, there are woefully few that meet the demanding criteria for this mission right out of the box. Besides being accurate and possessing utter reliability, a carbine designed for patrol work should be capable of mounting whatever accessories the officer deems necessary. A lightweight gun is especially appreciated if an officer is charged with holding a perimeter for a lengthy period, and the ability to adjust the buttstock to match armor/vests is also a necessity. Guns that use Mil-Spec parts make repairs easy and there is a seeminglyendless supply of parts. Walking the aisles of a recent gun show, I found a new carbine that meets all of those prerequisites.

Yankee Hill Machine (YHM), a company perhaps best known for their line of AR parts, accessories and suppressors is now offering complete rifles. One that I thought that makes perfect sense for police work is their brand new Black Diamond Specter XL.

I spoke with YHM’s Plant Manager, Paul Tetreault. “YHM decided that it was time to come out with our own line of AR rifles. Truthfully, what we were looking for was a platform that would showcase our line of accessories. We did not want to do a standard cookie cutter AR. So we built our models utilizing our accessory product line.”

Gun Details
yhm-black-diamond-specter-xl-556mm-cThe diamond-shaped cuts on the barrel allow for added stiffness and faster cooling, as well as provide a unique aesthetic.

The Black Diamond Specter XL features a 16-inch chrome-lined barrel, lightweight free-floating rail system, Mil-Spec receivers, bolt carriers and internals. Its upper receiver has M4 feedramps and all parts are hardcoat anodized per military specifications. The YHM rifle uses the standard gas impingement system. It’s a gun designed for hard honest use, devoid of gadgetry accessories yet possesses well thought out accoutrements that should make it perfect for the rigors of police work.


I couldn’t resist handling one of the Black Diamond Specters XL on display. As soon as I picked it up I was immediately impressed with just how light the gun was with this free-floated handguard system. The complete rifle weighs just 7.1 pounds, unloaded. According to Tetreault, “We skeletonized the rail system as much as possible without sacrificing strength. Since our logo is a diamond we decided to cut diamond pattern holes in the handguard. It is made from an extrusion and the rails are 100% machined. We decided to extend the rear so that it would meet up with the receiver and not have any gaps and would be in perfect alignment with the receiver top for mounting optics.” That is good news for those who like to mount their optics far forward, especially if they are using a magnifier and folding rear sight—this set-up provides plenty of room. Users have the option of mounting their optic partially on the upper receiver and partially on the rail. Each rail position is laser engraved.

YHM offers the Black Diamond Specter XL, the version I tested, and the Black Diamond Specter Carbine. Both weapons use a 16-inch barrel. The difference between the two models is that the Specter XL uses a rifle-length handguard. The most obvious advantage that I could discern is that it adds about 2 inches to the sight radius since the front sight is attached to the rail system rather than the gas block, which is covered by the handguard on both models. Tetreault says, “YHM’s Specter concept originated because of desire to streamline the rifle, giving it a sleeker look and feel.” YHM accomplished this by utilizing a low profile gas block that fits under the handguard.

Black Hills’ 50-grain V-Max bullets provided the best accuracy, producing a 5-shot group that measured just 0.87”.

YHM machines diamond-shaped cuts into the exterior of their barrels. While an argument can be made that these cuts increase surface area to make the barrel stiffer and cool faster while making it lighter, I think their real value is mostly cosmetic. Tetreault said, “We have barrels made to our spec and then we are doing the exterior cuts ourselves. The diamond flutes are CNC machined into the barrels exterior. Barrels are all chrome-lined with a chromed chamber. Users have a choice of a 1-in-7-inch or 1-in-9-inch twist and the chambers are cut to 5.56mm NATO specifications.” A nice touch is that YHM fits a cap on the front of their handguard. Its purpose is to keep all foreign matter out of the inside of the handguard. If you’ve ever carried a rifle with a free-floating handguard without an end cap in the field you know how much brush, twigs, mud, etc. can work their way into the handguard. The YHM endcap does not contact the barrel — it is free-floating.

Lower receivers are being made by YHM using forgings of 7075-T6 aluminum. Like other manufacturers, YHM hardcoat anodizes the lower receiver. If you’re looking for any magical differences between a YHM lower and other manufacturers, the only thing that I could find is that they flare their magazine well opening more than most. Internal parts are made from tool steel rather than MIM parts. Trigger pull on my test gun registered at 6.5 pounds — relatively clean with little creep and just a small amount of overtravel.

A standard M4 6-position buttstock is used on the Black Diamond Specter. The weapon is also fitted with an A2-style pistol grip. I’ve always hated that hook on the front of the pistol grip and replaced it with a Magpul MOE grip, which feels better in my hand.

I had YHM send my sample with their new Quick Deploy Sights. Both front and rear sights are low profile, designed to fold out of the way while using an optic. When the need arises, simply pushing a button deploys the spring-loaded sight into its upright and locked position. Pushing the button will allow the user to fold the sight again. The sights are made from aircraft-quality aluminum and hardcoated to military specifications. Rear sights are available with a single large peep, single small peep or dual peep aperture.

YHM outfits the Black Diamond with their Phantom Flash Hider/Compensator and a distinctive endcap on the free-float handguard.

Shooting Impressions

To test the rifle for accuracy I installed a Trijicon 3-9x AccuPoint scope and set my targets up at 100-yards. I fired all groups from a seated rest utilizing a cement bench and rifle rest for support from a hot barrel, five shots to a group. I was extremely pleased with the groups that the Black Diamond Specter XL produced. Heck, my largest group measured just slightly more than 1.50 inches. Black Hills produced the smallest group measuring just 0.87 of an inch with its 50-grain V-Max bullet. By the way, in guns with a 1-in-9-inch twist this particular load always seem to be the most accurate.

YHM’s Black Diamond Specter XL uses the standard gas impingement system and disassembles like any standard AR-15.

I received the Black Diamond Specter XL just in time to take a defensive carbine class taught by my good friend Ed Chavez. Chavez, a decorated Marine during the Vietnam Conflict and has just retired from the Tucson Police Department. He has spent the last four years of his career as a firearms instructor at the Southeastern Arizona Law Enforcement Training Center. When the Tucson Police Department decided to allow individual officers to carry patrol rifles on duty, Chavez was instrumental in helping design a qualification course. His Defensive Carbine class is based loosely on the class that each TPD officer must take before they are certified to carry their rifles.

For the class I needed to set the Black Diamond Specter up with a tactical sling. I installed a GG&G receiver end plate, which supplied me with a loop behind the receiver on which I could attach a single point Specter MOUT (Military Operations on Urbanized Terrain) sling. It’s a simple sling system that works effectively and is easy to adjust. With the male portion of the side release buckle attached to the weapon, and the female portion attached to the sling, the sling remains wrapped around the operator’s body when the release buckle is disengaged. This is the key feature of this design. If it becomes necessary to unhook the weapon from your body, such as when firing from an unconventional shooting position outside of the capabilities of the sling; or something as simple, yet hazardous, as mounting/dismounting a vehicle, there isn’t 3 feet of webbing trailing from the weapon. This allows the operator a much greater degree of versatility and safety.

Insight Technologies new Mini Red Dot Sight weighs less than an ounce, yet provides the shooter with a brilliant aiming point.

Chavez also recommended that I use some sort of optic during the class. I chose the new Insight Technologies Mini Red Dot Sight (MRDS). Weighing less than an ounce, the lightweight ruggedized reflex sight mounts directly to any Mil-Std-1913 rail. Insight Technologies offers this sight with both 3.5 MOA and 7.0 MOA size dots. I chose the smaller dot for better precision. After mounting the sight, I adjusted it so that the red dot was sitting on top of the front sight when looking through the rear aperture. The neat thing about the MRDS is that it windage and elevation adjustments are click adjustable. After folding down the sights and firing a group, I needed 3 inches of elevation and about 4 inches of windage left. I dialed these adjustments into the sight and fired another group that was perfectly centered.

The MRDS uses a top loading battery compartment that ensures no change of windage during a battery change. It uses a single 1632 battery that Insight claims will last up to a year in the auto-mode. The MRDS features an auto adjusting dot intensity but also offers the operator a manual dot intensity adjustment with four brightness settings. In several outings, including the defensive carbine class, the optic never failed and was always bright enough that I could easily find the dot when bringing the weapon on target.

Chavez had us confirm our iron sight zeros at 50 yards. My three-shot group measured about an inch and didn’t require any fine-tuning. He then had us repeat the procedure with our optics until everyone on the line was sighted in.


The day of the class was a typical Tucson winter day and while the temperature was comfortable and in the low 60’s the wind was absolutely brutal. We had gusts throughout the day ranging from 10 to 30 mph and the loose sand from the range floor worked its way into every nook and cranny of the Black Diamond Specter XL. I made a conscious effort to close the port door every opportunity I had, but this did little to help. Despite this, the Black Diamond perked right along without a bobble. Chavez had us fire a number of exercises—some slow fire and some rapid fire. Each break consisted of going back to the car and loading magazines. Before I knew it we had fired over 600 rounds. The Black Diamond Specter XL had digested over 800 rounds before I finally cleaned it. It was filthy, but cleaned up nicely and I detail-stripped the lower to get all of the sand out of it.

Final Notes

I was extremely happy with the way that the Yankee Hill Machine carbine performed. Its accuracy is outstanding and its reliability is exactly what is needed for a law enforcement patrol rifle. Its balance and lightweight give it fast handling characteristics that make it not so much of a chore to carry in a single point sling but very fast to put into action and get on target. It is a gun totally devoid of nonsensical gadgets and every feature and accoutrement seems to lend itself for use as a patrol carbine.

Machined from aircraft-grade aluminum and hardcoat anodized, the spring-loaded Quick Deploy Rear sight shown features dual apertures.

Years of manufacturing accessories for the AR market have fine-tuned Yankee Hills’ ability to give their savvy customers exactly what they are looking for. There’s nothing that I felt that I needed to replace on the rifle, other than the pistol grip — and that’s just a personal preference. Priced at $1,471 (with the Quick Deploy Sights), the Black Diamond Specter XL should make a great patrol carbine without the need for modifications.

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