For some, a skull can represent death, fear and even evil. For others, it symbolizes protection, strength, power, fearlessness and even wisdom. We assign meaning to objects to represent ideas or qualities, and “The Jack” AR-platform pistol from Spike’s Tactical and Sharps Bros. is meant to be a fearless, relentless defender. The Jack embodies protection and strength with a fearless aesthetic that is as awe-inspiring as it is functional.

In essence, The Jack is a specially designed lower receiver from Sharps Bros. with a screaming skull CNC-machined out of the magazine well. But this lower receiver isn’t just for looks. As John Sharps of Sharps Bros. said, “We add aesthetic features where there is room in the design for creative freedom as well as performance features like oversized triggerguards and flared magazine wells. We want it to look cool, but the bottom line is it needs to perform and function.”

spike's tactical jack ar pistol
The Jack’s most distinctive feature is the skull CNC-machined into the magazine well, which looks cool and helps speed up reloads. The teeth can even dig into a barricade or other support.

The magazine well has a flared edge so you can jam the teeth of the skull up against a barrier as a brace. The triggerguard is made for users wearing gloves—it’s large and oversized. Those are just a few examples of how this build masterfully combines form and function.

“The Jack was incredibly difficult to design, with multiple iterations and hundreds of man hours, and it is very time consuming to manufacture,” explained Sharps. We continued to talk about AR pistols and short barrels, gas ports, bolt dwell times—and then he started singing the praises of Paul Dettlaff, the chief operating officer at Spike’s Tactical, and his team of armorers. Spike’s Tactical also happens to be the sole distributor of Sharps Bros. lower receivers, and the two companies worked together to produce this incredible AR pistol.

AR-tistic Approach

sharp bros jack ar
Small details like the American flag machined into the right side of the billet-crafted upper help set these receivers apart in a crowded market.

Sometimes things that come in plain cardboard boxes are amazing. Unearthing The Jack AR from a shroud of bubble wrap and packing material, there was no doubt in my mind that Sharps Bros. and Spike’s Tactical had created an AR pistol that expressed the willingness and seriousness of what an AR pistol embodies. Such short-barreled guns with 30-round magazines can wreak havoc on those who wish to do us harm. The Jack is nothing less than a masterpiece of the AR builder’s art and science, because without science there is only beauty. With The Jack AR, the beauty isn’t just skin deep—it’s one badass pistol.

Building an AR-platform pistol is not quite as simple as chopping down a barrel and removing the stock. “There are a few variables to consider when doing an AR pistol build,” explained Wayne Warensford, head armorer at Spike’s Tactical. “Short barrels lose velocity and provide less dwell time for the projectile, so a lot more tuning and timing is involved.”

When Warensford designs an AR pistol, he usually starts with known quantities like the carrier weight, the buffer spring and the buffer weight, then sizes the barrel’s gas port accordingly. He also has to make the short-barreled pistol work with a broad spectrum of loads for the end-user, who may potentially feed it low-quality ammunition.

“Other factors that will change the gas port size are varying bore diameters between different barrel blank manufacturers and the type of muzzle device,” Warensford explained. “Most comps and brakes impart a backpressure which can aid in maintaining a smaller gas port. A flash suppressor will usually give you no backpressure, and that usually corresponds to a larger gas port. The reliability in a short-barrel AR comes from finding what I call the sweet spot in the tuning process.”

He continued, “Under-gassed and you will have feeding issues and the bolt won’t lock back after the last round is fired, but the shooter will have a feeling of reduced recoil. Over-gassed and you will also run into feeding issues due to the inability of the springs in the magazine to feed the next round in time. Another drawback of over-gassing is the timing being forced and the bolt actually ripping the case out of the chamber when it is under pressure and full expansion.”

According to Warensford, every AR has its balance point, and over years of testing, Spike’s Tactical has mapped these out for all barrel lengths and gas lengths for multiple calibers and incorporated this into its barrel manufacturing process. “These numbers are some of the most guarded secrets for most companies because they require hundreds of hours of trial and error and a bit of witchcraft to obtain. I keep most of these numbers in my cerebral cortex, and Spike’s is in major trouble if I drop dead in my cornflakes one morning.”

Lower Details

jack ar pistol
The billet-crafted lower receiver features a Spike’s Tactical Enhanced Battle Trigger, an enlarged triggerguard, KNS anti-walk pins and an ambidextrous safety selector.

As mentioned, The Jack offers fast reloads due to the flared magazine well, and the face of the skull offers a boney texture for a sure grip. Sharps Bros. builds The Jack and all of its receivers from billets of 7075-T6 aluminum and holds them to mil-spec or tighter tolerances. The Jack lower is fully compatible with all mil-spec magazines as well as Magpul PMAGs. The parts inside the lower, except for the Magpul MOE pistol grip, are all from Spike’s Tactical.

The Enhanced Battle Trigger (EBT) is manufactured from 8620 tool steel and hammer forged—it’s the only hammer-forged trigger group on the market for the AR platform. The disconnect is made from heat-treated 4140 chrome-moly steel with a slick and durable nickel-Teflon finish. The disconnect is also skeletonized—no pun intended—to reduce weight and increase the reaction speed for a quick and positive reset. The JP Enterprises 3.5T red hammer spring offers positive ignition even with harder primers while maintaining a crisp, ultra-smooth 4.5- to 6.5-pound pull weight. Spike’s installs the EBT with KNS Precision anti-walk pins so nothing comes loose during hard use.

The Spike’s Tactical Pistol Buffer Tube Assembly Kit features an integrated QD socket at the rear so you can mount your sling to it. The buffer tube also features a latch plate, a castle nut, a mil-spec 17-7 stainless buffer spring and an ST-T2 buffer. The company added its proprietary red/black pistol tube cover with its trademark spider for more visual impact.

Elite Upper

spike's tactical jack ar upper receiver
The upper receiver features an ultra-durable nickel-boron-coated bolt carrier group as well as a BCM Gunfighter Mod 4 charging handle with a heavy-duty latch for fast, one-handed manipulations.

The upper receiver is a Spike’s Tactical Gen II model crafted from a billet of 7075-T6 aluminum. The 8.1-inch, cold-hammer-forged barrel is paired with a pistol-length gas system. Melonited inside and out, the barrel has a 1-in-7-inch twist rate and comes fitted with Spike’s patent-pending Barking Spider 5.56mm muzzle device, which redirects noise, blast and concussion forward, away from the shooter. The device also increases the backpressure, which, in turn, can increase the reliability of a short-barreled setup where dwell time is sacrificed for barrel length. It also helps with subsonic or low-pressure ammunition.

Spike’s Tactical refers to the Barking Spider as a modular Krinkov-style muzzle brake since it can accept different end caps, attachments and thread protectors, allowing the user to tailor the weapon for specific applications. The front end of the Barking Spider integrates a striking device that would serve well for breaking glass. And in case you were wondering, it can handle full-auto and high-volume fire. This Jack, however, is a semi-auto pistol.

spike's tactical jack ar rail
The long top rail makes it easy to mount sights and accessories where needed, and the front of the Barking Spider is designed to work as a glass breaker or CQB standoff device.

Surrounding the barrel and gas system is a 10-inch M-LOK handguard with rail covers for a comfortable grip. A short Picatinny rail was attached for a tactical light or laser. Magpul MBUS Pro folding sights were also added.

The bolt carrier group is coated in nickel-boron, which is a super-durable finish that is smoother than hard chrome and easier to clean, and it makes the action cycle smoother. According to Spike’s Tactical, it can almost run lube-free for thousands of rounds, plus the finish won’t chip off. The bolt carrier group is machined from 8620 tool steel while the bolt itself is made from Carpenter 158 steel before being high-pressure (HP) and magnetic-particle (MP) tested. A BCM Gunfighter Mod 4 charging handle sets the bolt carrier group in motion.

Running The Jack

spike's tactical jack ar gun test

As good as it looks, the proof with any weapon is how it performs. I had a bunch of factory ammo boxes with two or three rounds left—not enough for collecting data, but enough to jumpstart The Jack. So I ran the pistol with a mix of 55- to 75-grain .223 Remington and 5.56mm NATO fodder, and I could feel the muzzle velocity difference between each cartridge type. If The Jack could speak, it probably would have said, “Is that all you got?”

I collected data on Aguila’s 62-grain FMJ rounds, Hornady’s 55-grain Steel Match HP ammo and Federal 62-grain Fusion MSR rounds. And I used the pistol’s Magpul sights just to experience The Jack in the raw, though a reflex sight would be a good addition.

At 25 yards and using a rest, my five-shot groups were all less an inch wide. The Hornady Steel Match ammo created groups closer to half an inch wide. The Jack ran flawlessly with mil-spec magazines, PMAGs and FAB Defense’s new Ultimag Smart Load magazines. I also used a BlackHawk single-point sling to steady the pistol as well as a Kydex magazine carrier from IBX Tactical with a skull and crossbones molded into it.

In the end, the crisp trigger and large, clear sights made aiming and firing The Jack AR a pleasant exercise, and racking the bolt carrier group was glass smooth. The pistol handled effortlessly with fast, fumble-free reloads. I’ve already waxed poetically on this build’s exquisite fit and finish; in operation, it was just as ruthlessly elegant.

For More Information

Sharps Bros.

Spike’s Tactical

This article was originally published in ‘Combat Handguns’ February 2017. To subscribe, visit

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