Skull Themed AR15 Build

300 blackout build- skull theme

.300 Blackout AR15 Skull Theme Pistol

After stumbling across the Sharp’s Brothers “Jack” AR-15 lower receiver, I decided it was motivation enough to start a project I had meant to create for a while. A .300 Blackout AR-15 build. Throughout this post, I will refer to what the SSP Firearm’s team did as a “build” on our Skull-themed AR15. Although, as it was pointed out to me and has stuck with me since, it was technically a part-buying journey and an “assembly,” not a “build.”

Below is a complete parts list of the project, and we will be releasing a video of the step-by-step process of the .300 skull-themed blackout build.

Skull-themed AR15 Build Video

Skull Themed AR15 Thank You’s

We learned a lot about planning and building an AR-15 on this journey and had some expert help from the team at Unique ARs for themed AR-15 builds; they are masters at the craft. They did the cerakoting work and built the custom handguard and buffer tube that brought this project to life.

The team at Unique ARs also did some amazing work on our Sharp’s Brothers Overthrow, Spartan theme AR15 Build.

A huge thanks go out to Matt, Alexander, and the whole team at Unique Ar’s for the great ideas and assistance on this build project and more to come!

Parts in this Skull-themed AR15 Build

.300 backout pistol parts

Keeping in mind, what many people consider parts on an AR-15 are major components, but factoring all the small parts 4 to 20 there are many more, so this list will seem comprehensive, but we wanted to cover every base. In a couple of cases, we bought preassembled parts because we had an affinity with the manufacturers of those components, and that is how they sell their products.

For specifications on any part in this build, you can click the “Specifications” drop-down below each photograph.

Upper Receiver

The upper receiver is the top half of a receiver in the AR-15 firearm platform. The barrel attaches to the front of the upper receiver, and the bolt carrier group resides in the rear of the upper. The upper receiver has several additional parts; below is a list of those parts and a parts list of what we used in our build.

The Upper Receiver was assembled for our build, but if you purchase a stripped upper receiver, you will also need to buy other parts.

  • Forward assist
    • forward assist detent
    • forward assist pawl
    • forward assist pawl roll pin
    • forward assist pawl spring
    • forward assist pin
    • forward assist spring
  • Ejection- port cover
    • ejection port snap ring
    • ejection port cover pin
    • ejection port cover spring

B.A Enhanced

Forged from 7075-T6 aluminum, this assembled upper is precision machined to mil-spec M16/M4 specifications and features M4 feed ramps.

  • Threaded Forward Assist Roll Pin – Allows for simple installation of the forward assist and eliminates the chance of damaging the finish during installation (pin included).
  • M4 Feedramps
  • .250 takedown pin holes
  • Lazer engraved T-marks
  • Ballistic Advantage branded
  • AR15 Assembled Upper Receiver in Anodized Black
  • Features:
  • New enhanced forging gives the upper receiver a “billet look.”
  • New Picatinny profile that blends seamlessly with our Enhanced Lowers.
  • M4 Feedramps
  • .250 takedown pin holes
  • Laser engraved T-marks
  • Includes threaded forward assist roll pin
  • Include port door or forward assist

Bolt Carrier Group

The AR-15 bolt carrier group (or “BCG”) is the part in the upper receiver of the AR-15 that facilitates the firing of a round when the trigger is pulled. The bolt carrier group houses the following components.

  • Bolt
    • Bolt Cam Pin
    • Bolt carrier
    • Bolt key
    • Bolt key screws
  • Ejector
    • Ejector pin
    • Ejector spring
  • Extractor
    • Extractor pin
    • Extractor spring
  • Firing-pin
    • Firing pin
    • retaining pin
  • Gas-rings

Note: Bolt carriers come striped and with components. When you do your build, be sure your “BCG” has all the components or sources additional components to add to your bolt carrier group.

BA 5.56 Bolt Carrier Group

Ballistic Advantage bolt carrier group
  • M16 Carrier Machined from 8620
  • 5.56 Bolt Machined from 9310
  • Forged Gas Key Properly Staked
  • Tool Steel Extractor
  • Mil-Spec Extractor Spring with a black insert and Viton O-Ring
  • Grade 8 hardware
  • Shot Peened Bolt
  • Carrier, Gas Key, Cam Pin, Bolt, and extractor coated inside and out with Black Nitride QPQ
  • Test Fired complete before shipping to ensure proper function

Charging Handle

The charging handle on the AR-15 is used to load the initial round into the chamber and prepare the firearm to shoot. When pulled, the charging handle pulls the bolt carrier group from the front of the receiver to the back, which opens the breech, and cocks the hammer. When the charging handle is released, the bolt strips a round from the magazine and loads it into the chamber.

Most charging handles come with all parts prebuilt, but if you purchase a kit, ensure the following components are included.

  • charging handle
  • charging handle latch
  • charging handle latch pin
  • charging handle
  • latch-spring

Radian Raptor-SD Charging Handle AR15

Radiant charging handle

The silencer-optimized Raptor-SD™ features a ported shaft designed to redirect gasses down and forward, away from the shooter’s face when shooting suppressed. Its ambidextrous design allows rapid palm “blading” or finger-thumb charging of the weapon, ensuring the motion is fluid and fast from either the strong or support side. The Raptor-SD is compatible with most AR15/M16-pattern rifles. • Designed & Manufactured in the USA • Machined from 7075-T6 aluminum • MILSPEC Type 3 Hard Coat Anodized Finish w/ Cerakote Color Options

Ejection port cover-dust cover

They keep dust and debris out of the bolt/chamber area. The ejection port is on the right side (looking down at the rifle) and opens after the first round.

The ejection port or dust cover is comprised of the following parts.

  • ejection port cover
    • ejection port snap ring
    • ejection port cover pin
    • ejection port cover spring

Ejection Port Dust Cover

MST AR-15 Ejection Port Dust Cover


Custom Magpul enhanced polymer quick install ejection port dust cover for AR-15 rifles and pistols. The design has been professionally applied to the surface for a vivid and durable finish. Dust covers are made of the same polymers as all of our custom PMAGs, which have been proven to last through the most demanding environments.

No more messing around with springs, rods, and those pesky clips to install a new dust cover.

Compatibility: Compatible with Mil-spec AR15 upper receivers that accept USGI ejection port covers. Known Fitment issues with Aero Precision ENHANCED Uppers: Please research to ensure your rifle is compatible.

Please select whether you want the image applied to the inside, outside, or both using the selection box above.

Forward Assist

The forward assist enables a shooter of an AR-15 to quickly close the bolt if a cartridge fails to chamber correctly. A mis-chambered round will hold the bolt open until it is fixed, and the forward assist facilitates solving the problem.

The forward assist is comprised of the following parts.

  • forward assist
  • forward assist detent
  • forward assist pawl
  • forward assist pawl roll pin
  • forward assist pawl spring
  • forward assist pin
  • forward assist spring
forward assist

Custom AR15 skull theme Photos


The barrel is the primary component in an AR-15 that determines the caliber(s) the firearm supports. The barrel specification defines the distance the round is capable of traveling and the level of accuracy.

Barrel parts include.

  • Barrel and Barrel Extension
  • barrel nut barrel retaining ring
  • compensator
  • peel crush washer

10.3″ .300 Blackout BA Hanson Barrel

BA 300 Blackout

This .300 Blackout chambered 10.3-inch Performance Series Barrel is machined from 4150 Chrome Moly Vanadium steel with a QPQ Corrosion Resistant Finish. Our Performance Series Barrels feature a Nickel Boron Coated M4 Feed Ramp Extension and are HP and MPI tested

Hanson Series Barrels feature our proprietary BA Hanson profile and include a pinned lo-pro gas block. Hanson barrels are not designed to work with aftermarket piston kits.

All NFA/ATF Rules Apply
You may use this barrel with a lower receiver that is a Registered SBR, Machine Gun, or Pistol. Possession of this barrel and a Non-NFA lower receiver is Prohibited, except when installed on a Pistol configuration firearm.

Gas System

The AR-15 gas system controls the hot gasses generated when a rifle fires a round. Gasses are led to the gas block through a small port in the barrel, run through the gas tube along the barrel, and to a port in the bottle carrier group. The force of the gas propels the bolt carrier group back, ultimately responsible for forcing the spent casing out and cycling a new round into the chamber.

BA Adjustable Lo-Pro Gas Block

gas block, gas tube


The AR 15 handguard is installed onto the upper receiver. Further, it surrounds the barrel to protect the shooter’s hands from the heat generated by the barrel, and further, with rails either added or built into the handguard, accessories such as lights, lasers, scopes, red dots, bipods, and more can be equipped the to the rails.

Unique-AR’s “One Shot” Handguard

one shot handguard by unique ars

Free-float handguard made of 6061 T6 Aluminum
Inside diameter 1.75″, exterior diameter 2″
Compatible with any mil-spec AR-15 upper receiver or (DPMS Gen 1 Style) AR-10 upper
Mount accessories with Unique-ARs proprietary Picatinny rail only

Heat Shield

The heat shield provides a thermal barrier between the barrel as it heats up, and the handguard

Unique AR Heatshield


Heat shields install by sliding under the Original Series Handguard and over the AR-15 castle bolt. They are tightened down to the barrel with the included end cap that will replace your muzzle brake.

It is only compatible with barrels of these exact lengths and low-profile gas blocks that are the same width and height as the ones available on this website.

The pocket length for a gas block on heat shields is as follows:

Pistol 5.5″ from the face of the upper.
Carbine 8.5″ from the face of the upper.
Midlength 10.5″ from the face of the upper.
Rifle length 13.5″ from the face of the upper.

Sights and or Optics

Sig Sauer ROMEO7 1X30 MM

Romeo optics

The ROMEO7 full-size red-dot sight provides the civilian and armed professional with a robust 1x aiming solution optimized for today’s MSR platforms, regardless of caliber. The battery life lasts an incredible 62,500 hours (on medium setting), and the low AA battery compartment allows for quick battery replacement without removing the sight from the firearm. The high-performance lens coating provides excellent light transmission, zero distortion, and the highest possible dot brightness. Features Low Dispersion (LD) glass lens design with high-performance coatings for superior light transmittance and zero distortion. The 2 MOA dot is optimal for the close-quarters battle to mid-range target engagement.

-Low Dispersion (LD) glass lens design with high-performance coatings for excellent light transmittance and zero distortion
-2 MOA dot is optimal for close-quarters battle to mid-range target engagement.

  • CNC machined 6061 aluminum body for extreme ruggedness and durability
  • Manual illumination controls
    -MOTAC™ (Motion Activated Illumination) powers up when it senses motion and powers down when it does not. Provides for optimum operational safety and enhanced 62,500 hours of battery life in a medium illumination setting
    -Ready to mount with a low profile cross bolt M1913 STANAG-compliant mount and 1.535″ QD riser mount.
    -Dependable waterproof (IPX-7 rated for complete water immersion up to 1 meter) and fog-proof performance

Lower Receiver

The lower receiver is the bottom half of the AR-15 receiver. It houses the fire control system (trigger), safety selector switch, bolt catch release, magazine release, and the buffer and pistol grip attached to it.

Sharp’s Brothers “The Jack”

ar-15 lower reciever

An oversized integral trigger guard
A beveled magazine flare that helps you load as quickly and efficiently as possible
Machined top to bottom from 7075-T6 aluminum, a peak-strength corrosion-resistant aluminum alloy
A hard coat anodize finish per MIL-A-8625, the anodizing model for most military and aerospace products.
Full compatibility with all mil-spec internal parts, all other aftermarket mil-spec upper receivers and PMags, Hex mags, and other standard capacity magazines
Multi caliber mark
Weight: 10.7 oz

Trigger Assembly

Commonly referred to as the trigger, the fire control group is the first step to discharging an AR-15.

It has of the following parts.

  • disconnector
  • disconnector spring
  • trigger
  • trigger guard
  • trigger guard roll pin
  • trigger pin
  • trigger spring

Fostech Echo AR II Binary Trigger

Safe Mode: Will not fire.
Semi-Automatic Mode: Fires when the trigger is pulled.
Echo Mode: Fires when the trigger is pulled and also when the trigger is released.
The Echo II Trigger is designed to work with direct impingement AR-15 rifles and pistols. This is the Gen II variation, the latest and most advanced version of the Fostech Echo triggers. The original Echo required a separate bolt carrier to function. Still, this Gen II trigger will work in any direct impingement AR-15 rifle utilizing a full auto bolt carrier with which virtually all ARs are currently being produced. It provides a clean, crisp trigger pull regardless of the selected firing mode, and the trigger pull in semi-auto mode is as good as, if not better, than most standard mil-spec triggers. The ATF fully approves the Echo II trigger.


H buffer – Ensure that when you shake the buffer, it rattles.

Some lower receivers have a sear block or wall; the sear wall will prevent the trigger from functioning as designed.

The wall of extra material causes the trigger lock to remain compressed forward and can cause improper fitment of the selector switches.

Large trigger pin lower receivers are not compatible. The Echo ARII Trigger uses standard trigger pins. You are welcome to use anti-walk pins if you would like.

Most Carbon Fiber or Polymer Lowers have extra supports. Extra supports that get in the way of the trigger pack are not compatible.

Pistol Grip

Located on the back of the lower receiver behind the trigger guard, the pistol grip allows for a comfortable handle when firing your AR-15. Parts of the pistol grip are.

  • pistol grip
  • pistol grip lock washer
  • pistol grip screw

Unique Ar’s Unique-Grip

unique ar pistol grip

This customizable Unique Grip perfectly conforms to each shooter’s hand, regardless of size, shape, strength, or dominance. This ergonomic pistol grip adjusts precisely to your hand to reduce fatigue and improve performance. The patented grip functionality allows it to compensate for the natural twist of every shooter’s hand. Instant fit, instant comfort. This grip easily installs on all mil-spec AR platform rifles. Grip it, lock it, and fire away. Weight is 4.2 oz.

Buffer Tube

Buffer tubes house the AR15s buffer and the recoil spring and are attached to the lower receiver. Parts included in the buffer tube are.

  • buffer assembly
  • buffer retainer
  • buffer retainer spring
  • buffer spring
  • buffer tube
  • butt stock
  • receiver end plate

Unique Ar’s One Shot Buffer Tube

Unique Ar's One-Shot Buffer Tube

The perfect addition to your AR pistol. Pair with a One Shot handguard to add balance to your build.

This kit includes a custom buffer tube, Gear Head Works Tailhook Mod 1, Pistol End Plate, and End Cap.

When this item is on backorder, please allow 2-4 weeks for production.

Buffer System

The buffer system in an AR-15 helps return the bolt carrier group as the gas system pushes it back.

Aero Precision AR Carbine Buffer Kit

AR15/AR10 Enhanced Carbine Buffer Tube Features:

The Carrier Support Extensions also extend on either side of the buffer retaining pin, securing the pin in place while simultaneously preventing the buffer tube from backing out under the recoil.

Position Guide Drain Holes – Each position guide features a drainage hole that removes water from the system in marine environments.

Ramped Tube Design – Allows for effortless installation of traditional carbine stocks. We have removed the need for messing around with screwdrivers to get your furniture over the end of the buffer tube. Instead, hold down the adjustment piece and push your stock onto the Enhanced Buffer Tube.
Proper Thread Depth – Traditional buffer tubes feature extended new threads that can cause your stock to become trapped when entirely collapsed. While some turn these threads down, we’ve correctly machined the threads to the proper depth, providing a much cleaner look.

Mil-spec Dimensions – Machined from a 7075-T6 Aluminum Impact Extrusion to mil-spec dimensions. All standard carbine stock options that work with mil-spec buffer tube dimensions are compatible with our Enhanced Carbine Buffer Tube.

Enhanced Carbine Buffer Tube, 6-position
Carbine Buffer
Carbine Buffer Spring
Endplate and lock nut

Butt Stuck

The AR-15 butt stock is part of the AR closest to the shooter.

Gear Head Works Tailhook Mod 1

Arm Brace

The Patented Tailhook MOD 1 is the most compact pistol brace in the world. Depress the release button and pull the arm down to activate the brace functionality. This creates a shelf that will counterbalance the muzzle weight of your large-frame handgun. The ability of your forearm to hold the weight allows you to relax your shooting wrist and concentrate on trigger control. The Gear Head Works Tailhook Mod 1 does not have a QD Swivel mount.

More Custom AR-15 in skull theme Photos

Skull-themed AR15 Trouble-shooting.

Update: 1/14/23- We got the Skull-themed AR15 out to the range a few times now and have a bit of an under-gassed problem.

It shoots and cycles excellently but doesn’t lock back after the last round. Despite our best efforts, the issue of the bolt carrier not locking back remains unresolved. We have tried several solutions and continued to test others to find a solution.

Tested So Far

It was functioning correctly and properly engaged with the bolt catch. We also tested the bolt catch itself to determine if it was engaging correctly and working as intended. Additionally, we checked the spring tension on the magazine to ensure that it was adequate and not causing any issues.

We are currently exploring other potential causes of the problem, such as the ammunition used, the gas system, or the buffer weight.

Gas System

  • Check the gas system: We did a preliminary inspection of the gas tube; it is not blocked, and the gas key on the bolt carrier appears to be properly staked. Although we are not convinced this isn’t the culprit, and will come back to this if none of the other potential issues solve the problem. Below is the plan for confirming gas system checks out.
  • Remove the upper receiver from the lower receiver.
  • Inspect the gas tube for any blockages or damage to make sure it is properly aligned with the gas key on the bolt carrier.


  • Check the gas block for any blockages or damage. Make sure it is correctly tightened to the barrel.
  • Inspect the gas key on the bolt carrier for proper staking. The gas key should be firmly secured to the bolt carrier with small indentations around the mounting screws to prevent it from coming loose.
  • Reassemble the upper and lower receivers and test the gun by firing a few rounds. One possible solution is to try a different gas system configuration. This could involve experimenting with a different-sized gas port or a different-length gas tube, depending on the specific issue at hand.


  • Measure the gas tube length: Using a caliper or a ruler, measure the length of the gas tube from the gas block to the gas key on the bolt carrier.
  • Compare the measurement to the manufacturer’s specifications: Check the manufacturer’s specifications for the recommended gas tube length for your gun. If the gas tube length on your gun is significantly different from the recommended length, it could be causing the under-gassing issue.
  • Check for proper alignment: Ensure the gas tube is aligned with the bolt carrier’s gas key. If the gas tube is not aligned with the gas key, it may not send enough gas pressure to the bolt carrier to cycle the action.
  • Test the gun: If you have checked the gas tube length and alignment and the gun is still not functioning properly, you may need to try a different gas tube length or a different gas system configuration.

Bolt Catch

  • Check the bolt catch: This is next on our list and the plan is as follows;
    • Check the bolt catch for damage. If the bolt catch is damaged, it may be unable to hold the BCG open after the last round.
    • Check the bolt catch spring for damage. If the bolt catch spring is damaged, it may not have enough tension to hold the bolt catch in place.
    • Check the bolt catch roll pin for proper installation. When bolt catch roll pin is not properly installed, the bolt catch doesn’t function correctly.
    • Test the bolt catch by manually releasing the BCG and pulling the bolt catch up to hold the BCG open. If the bolt catch is not able to hold the BCG open, its likely damaged or improperly installed.


  • Check the buffer and spring: We are using the recommended weight buffer and buffer springs but will do the following testing.
    • Check the buffer weight: Make sure the buffer is the correct weight for your gun. An excessively heavy or light buffer can cause issues with the cycling of the action.
    • Check the buffer spring to ensure it is not damaged or excessively worn. If the buffer spring is damaged or excessively worn, it won’t provide enough tension to cycle the action properly.
    • Test the buffer and spring by manually releasing the BCG and pulling the charging handle to the rear. If the action is smooth and the BCG stays back when released, the buffer and spring are likely functioning correctly. However, if the action is not smooth or the BCG does not wait back when released, the buffer and spring may be causing the issue.

Once we have executed these plans and things are working as they should, we will update this post with the solution that solved the problem. Stay tuned to the blog for next week’s Iridescent AR15 build post.

AR15 Build FAQs

Is it legal to build my own AR-15?

Yes, it is legal to build your AR-15 as long as you comply with all federal, state, and local laws. For example, in the United States, federal law allows individuals to build firearms for personal use as long as they are not for sale or transfer.

Can I mix and match parts from different manufacturers when building an AR-15?

Yes, you can mix and match parts from different manufacturers when building an AR-15, but ensuring all the parts are compatible and will work together correctly is essential.

Do I need any special tools to build an AR-15?

Yes, you will need some special tools to build an AR-15, including a set of roll pin punches, a vise block, an armorer wrench, a torque wrench, and a headspace gauge. Some of these tools can be expensive, so you may want to consider purchasing them as part of a kit or borrowing them from a friend.

How much does it cost to build an AR-15?

The cost of building an AR-15 can vary widely depending on the quality and type of parts you choose. You can build a basic AR-15 for around $500, but a high-end custom build can cost several thousand dollars.

Is it difficult to build an AR-15?

Building an AR-15 requires some mechanical knowledge and basic gunsmithing skills, but it is not overly difficult. There are many online resources and videos available to help guide you through the process. Follow the instructions carefully.

Is it hard to clean an AR15?

Cleaning an AR-15 is not particularly difficult, but it does require some time and attention to detail.


  • Michael Hodgdon

    A firearm, shooting, outdoor, and hunting enthusiast for over 35 years. Thank you all for the suggestions on topics you would like to see; we'll keep posting as you keep sending them in. Please comment; we will try to answer all comments quickly.

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