Diamondback Firearms  of Cocoa, Fla., was established in 2009 and has the distinction of making some of the smallest striker-fired pocket pistols you can get. The Diamondback DB380 and DB9 pistols are truly innovative and well made. I have tested both of them and came away impressed, so I was all the more enthusiastic to get a chance to try the company’s new AR rifles as well.

• RELATED: Diamondback DB15 5.56mm
• RELATED: Diamondback DB9 9mm

The company’s recent entry into the AR market with both rifles and pistols marks a significant expansion of its firearms lineup. Diamondback originally started out producing airboats for navigating the Florida swamps, a successful business the company stills operate.

Diamondback’s line of DB15 rifles comes in seven different flavors distinguished by their different finishes, furniture and features, including a base model with no forward assist or dust cover. The higher-end model I recently got the chance to test is the DB15NIB rifle, which features very distinct upper and lower receivers that, along with the bolt carrier group, have a nickel-boron finish. This is a semi-automatic, carbine-length AR chambered in 5.56mm NATO with the standard direct gas impingement operating system.

Tank Tough

With a Rockwell hardness rating of 70, nickel-boron is a compound that is harder than chrome while having lubricity and friction-reducing qualities similar to Teflon. It also provides extreme corrosion resistance. In its natural state, nickel-boron has a natural matte silver color, but it can be polished bright or ceramic coated in any color. Its natural lubricity means that ARs with nickel-boron-coated bolts can run dry and are much easier to clean. The carbon fouling can literally just be wiped off. Less friction also means less heat, and the nickel-boron finish has its own heat-dissipating properties as well.

“Its natural lubricity means that ARs with nickel-boron-coated bolts can run dry and are much easier to clean.”

The DB15NIB’s upper receiver is forged from 7075-T6 aluminum and hardcoat anodized. Then the nickel-boron finish is applied over the anodizing. The flattop upper receiver comes optics-ready with no sights and features T-markings on top. These allow the user to more easily return optics to the correct spot if they are removed, helping to preserve their zero. As with the lower receiver, parts like the dust cover, forward assist and charging handle are left black. This black/silver contrast is very attractive.

The 16-inch barrel has an M4 profile and is made from 4140 chrome-moly steel. It has a 1-in-9-inch twist rate to stabilize light- to medium-weight bullets effectively. To clarify, this means that the rifling provides the bullet with one complete turn for 9 nine inches of barrel length. The DB15NIB has a carbine-length gas tube, and the barrel is capped with a removable A2-style flash suppressor.

The barrel also remains free-floating thanks to the Diamondback aluminum quad-rail handguard. Free-floating the barrel helps to improve accuracy, as the barrel remains free from any external strain or pressure that could affect shot consistency. This handguard provides a full-length Picatinny rail on top that melds almost seamlessly with the flattop upper receiver’s for over 14 inches of continuous rail space for optics and laser systems. The sides and bottom of the handguard are very smooth for user comfort, and 2-inch rails are included at the 3, 6 and 9 o’clock positions at the font of the handguard. This makes it easy to mount a vertical foregrip or bipod as well as weapon lights or lasers. Sling swivel attachment points are included at the rear of the handguard on both sides—another nice touch.

Internally, the Diamondback AR features a completely nickel-boron-coated bolt carrier group—even the small parts have been treated. The coating has been polished bright, which helps to increase its lubricity. Indeed, I ran the rifle dry during all of my testing and never had any malfunctions. At the end of two days of testing I was able to easily wipe away the carbon fouling on the bolt with a dry towel. The bolt carrier group is all mil-spec and made from 8620 steel that has been shot-peened and magnetic-particle (MP) inspected.

Shot-peening is a type of sandblasting using metallic shot that works on the plasticity of the metal rather than as an abrasive. This provides compressive stress to the bolt surface, increasing metal fatigue resistance and extending the operational life of the part. MP testing is only required of true mil-spec parts. This consists of using a magnetic field to detect any imperfections in the surface or subsurface of the part, ensuring that only the highest-quality parts are being used. The gas key has also been carefully staked using a hammer and punch with enough force to move sufficient metal into the carrier key screws. If these screws are not properly staked, they could become loose under fire.

M4 feed ramps are also provided at the rear of the barrel extension. Unlike the feed ramps on a standard AR, M4 ramps are cut wider and lower, extending past the back of the barrel and into the receiver. This helps ensure more reliable feeding from the magazine under harsh conditions. I have seen these ramps cut deeper by some manufacturers and found those in the Diamondback a bit shallow but still effective.

A Look At The Lower

The lower receiver is forged from 7075-T6 aluminum, hardcoat anodized and then given the nickel-boron finish. There is a standard steel safety selector on the left side that operates with a resounding click, and the “safe” and “fire” markings are on both sides. All of the controls are set up for standard right-handed operation, and all of the pins and small parts are left in black, offering a nice contrast against the bright nickel-boron coating. The triggerguard is polymer instead of aluminum, and rotates down for gloved use in the mil-spec fashion.

The Diamondback logo is visible on the left side of the receiver, but all of the other receiver markings, including the serial number, model name and manufacturer’s information are located on the right side, opposite what one usually sees. The caliber designation on the rifle is listed as “multi” which more easily allows for caliber conversions.

The rest of the furniture has also been upgraded, starting with a Magpul MOE+ grip. This grip really fills the hand and features a beavertail that brings the trigger finger more naturally in line with the trigger. It also features ample internal storage space for spare parts or extra batteries and has a rubberized overmolding for a superior grip even in inclement conditions.

The six-position-collapsible Magpul CTR stock offers enough adjustment to fit shooters with varying statures for those wearing heavy clothing. Adjustments can be made very quickly and easily, and the stock also has a simple locking device to keep it in the user’s preferred position. A rubber buttpad keeps the stock firmly and comfortably on the shoulder, and there are plenty of sling-mounting options, including an ambidextrous sling swivel attachment point.

DB15 Downrange

The DB15NIB’s fit and finish are excellent, with no play between the upper and lower receivers. The rifle also felt lightweight and, combined with its short length, it was easy to handle on the range with minimal recoil and fast follow-up shots.

The trigger was a standard mil-spec, single-stage variety, with roughly an 8-pound pull weight. It did exhibit minimal take-up but a fair amount of creep. The rifle’s accuracy potential could be improved by replacing the trigger with any of the several aftermarket drop-in trigger kits that offer crisper and lighter trigger pulls.

To wring out the rifle’s accuracy, I tested the DB15NIB from a benchrest at 100 yards using a Trijicon 3-9x40mm AccuPoint scope with an illuminated mil-dot reticle. Its accuracy was solid for a patrol or sporting rifle. My best group was just larger than 1 MOA at 100 yards, and the rifle showed a distinct preference for the Federal 69-grain BTHP ammo overall.

Ready To Strike

Diamondback has delivered a well-built, attractive and extremely reliable rifle with its DB15NIB, and the nickel-boron coating is a welcome addition. Over two days of shooting, I experienced no malfunctions, firing the rifle right out of the box with zero maintenance performed between sessions. You get quite a bit for your money, and the rifle ships with a 30-round Magpul magazine, a user manual, a cable lock and a chamber flag—all packed in a well-built, hard-sided case.

For more information, visit diamondbackfirearms.com or call 877-997-6774.