Join the 10.3″ Master Race, Build a MK18

Step with me into the wormhole that is MK18 Clone and Clone Inspired Rifle or Pistol Building. These clone inspired builds include CQBRs (Close Quarters Battle Receiver) Block 1 and Block 2, MK18s Mod 0 and Mod 1, or the URG-I (Upper Receiver Group Improved) that was just introduced to the United States of America Special Operations Command. That’s why we have took the initiative to provide a comprehensive guide and include as many parts as possible to assist those wishing to complete their clone inspired builds without breaking the bank as an exact replica using premium parts clone correct parts from Colt, Crane, Daniel Defense, & Knights Armament Co. could end up putting quite the strain on your average builders wallet! This by no means is a budget build but we did our best to provide you with the best options without sacrificing quality. At the end of the day this build isn’t meant to be flashy. Its meant to do work. By not cutting any corners with cheaply manufactured parts it will run circles around those Gucci ARs that are plaguing ranges across the country without skipping a beat!

With that said lets get started.

Photo Credit: Used with permission from @pewfessional on instagram.


Many variations of the MK18/CQBR/ URG-I used the Colt or USGI contract M4 flattop.  Again, you can probably go hunt one of these down but its going to cost you some serious cash. But for the clone inspired build Just a standard Milspec flatop receiver wll suffice.

Tactical Shit Stripped Upper

A forged upper built to the same Mil-Spec standards you require for your build, with the Tactical Shit Gun Spartan etched on the top rail

This is the same mil-spec forged upper used by many builders and manufacturers today.

With the well known Tactical Shit Gun Spartan logo on top.

  • Forged 7075 T6 Aluminum
  • Black Anodized
  • M4 Feed Ramps
  • Shell Deflector
  • Forward Assist & Dust Cover Ready

Charging Handles

M84 Gas Buster® Charging Handle -Military Big Latch

The Gas Buster® charging handle is a safety device with ergonomic design that diverts harmful gases, oil and dirt particles away from the shooter. The gas buster comes with Big Military latch. This is a PRi Patented product. Safety approved & used by the US Marine corps.  The charging handle is constructed of T6 7075 hard coat black anodized aluminum with a steel latch.

Bolt Assembly

This is where it gets fun. All of the variations used a Milspec contract M16 BCG. However, there were a couple changes made the standard gas rings on the bolt itself was replaced with a Mcfarland style gas ring and the extractor received an upgraded spring and insert.

BCM Extractor Spring Upgrade Kit

The BCM Extractor Spring is a heavy coil design made for the increased extractor tension required on many AR15, M4, M16 short barreled rifles. This product also improves the reliability on a standard 16″ and 14.5″ carbines. As with all BCM branded products, the highest quality is the primary focus. The BCM Extractor Spring is manufactured by a 9001:2000 facility employing the latest precision equipment. BCM starts with only the highest quality chrome silicon material, heat treats to stress relieve the product and shot peens to add increased strength.

This kit also includes the new black extractor insert, standard on all M4, M4A1, Mk18 carbines and the recent new standard on M16A4 rifles. The BCM Extractor Spring is so strong the Mil-Spec Crane O-Ring will probably not be needed, but it is included.
This kit includes:
– BCM Extractor Spring (chrome silicon, heat treated & stress relieved, shot peened)
– Crane Ind O-Ring (Mil-Spec)
– Black Extractor Insert

BCM FLAT DARK EARTH Bolt Carrier Group MPI Auto (Comes with extractor insert!)

BCM® (MPI) complete bolt carrier group is fully assembled. (BCG) Bolt carrier group (auto version) for your AR15, M16, or M4. The carrier is finished in an Ion Bonded Flat Dark Earth. Lowers friction and cleans easier.  Parkerized exterior and chrome lined inside carrier. Machined to USGI specifications. This M16/M4 carrier includes the proper Mil-Spec gas key. Gas key is chrome lined and heat treated per GI specifications. Gas key is secured to carrier via USGI domestic mfg Grade 8 fasteners and properly staked per Mil-Specs. These properly hardened parts ensure a strong staking and proper gas system functioning.

The bolt assembly is machined from the correct Mil-Spec Carpenter No. 158® steel, shot peened for increased strength, includes tool steel machined extractor and ejector, BCM Extractor Spring, and is HPT (High Pressure Tested) and MPI (Magnetic Particle Inspected).

Prior to shipping, all BCM Bolt Carrier Groups are test fired for function. As such, the Bolt Carrier Group will show handling marks consistent with these quality control procedures.


  • Milspec Carpenter No. 158® steel
  • HPT Bolt (High Pressure Tested/ Proof)
  • MPI Bolt (Magnetic Particle Inspected)
  • Shot Peened Bolt
  • Chrome Lined Carrier (AUTO)
  • Chrome Lined Gas Key
  • Gas Key Hardened to USGI Specifications
  • Grade 8 Hardened Fasteners
  • Key Staked Per Mil-Spec
  • Tool Steel Extractor
  • BCM Extractor Spring
  • Black Extractor Insert
  • Mil-Spec Crane O-Ring

F-1 5.56 Durabolt Bolt Carrier Group-DLC

The F-1 Firearms DuraBolt direct impingement full auto rated M16/M4 bolt carrier group, for use in AR15 platforms, is compatible with MIL-SPEC receivers and associated components. The DuraBolt  is enhanced with a Physical Vapor Deposition (PVD) coating, which gives it an extremely durable and corrosion resistant silver mirror finish. The DuraBolt  coating also offers excellent lubricity with a low coefficient of friction.

  • Carpenter 158 bolt, ground after heat treat, MPI and HPT
  • 9310 steel carrier, ground after heat treat
  • Due to current demand, please allow up to 30 days for shipment
  • Available in Gold Tin, Silver, Rose Gold, and Black Nitride


Grips are another part that varied between the models. The MOD 0  used a standard A1 grip while the CQBR block 1 used a  used either an A1 or A2. Mod 1 and CQBR block 2 were one of the parts the started to include the use of the Magpul MIAD and MOE grips at the users request along side the standard A2 grips.


Similar in concept to the MOE-K, the MOE-K2 (Magpul Original Equipment) is a drop in upgrade for AR15/M4 pistol grips with a more vertical grip angle optimized for short LOP weapons that bring the primary hand in closer to the shooter’s body.

With an aggressive new texture for positive weapon control, compatibility with optional Storage Cores for gear stowage, and a unique backstrap design for proper trigger finger placement, the K2 brings modern styling and ergonomics to the AR platform.

Magpul MOE Plus AR 15 Grip

Magpul Original Equipment(MOE) products are low-cost, high quality alternatives to standard weapon components, designed to provide essential enhancements to weapon performance and usabilty. The MOE line distiguishes itself with a simplified feature set, but maintains Magpul engineering and material quality.

  • Drop in upgrade for AR15/M16 pistol grip
  • Rubber overmold on reinforced polymer construction
  • Hard polymer bottom edge prevents snags and grip damage
  • Storage core capability accepts optional cores
  • Designed to improve ergonomics and weapon control


Hand guards will vary depending on which you decide to build. The URG-I for instance uses a geissele mk16 9″ handguard which only seem to be available on their newly released URG-I upper receivers.  However there are a few substitutes that will get your clone inspired build close should you choose to build your upper. The MOD 0 and CQBR Block 1 used the KAC  M4 RAS while the MOD 1 and CQBR Block 2 moved on to the Danilel Defense M4 rail.

Daniel Defence M4 Rail 9.0 MID – LENGTH

The Daniel Defense DDM4 Rail features an optimized one-piece, free-floating architecture. This design results in the ergonomics and proven durability users demand while maintaining the lightweight characteristics they expect from Daniel Defense. The DDM4 Rail’s ergonomic design allows operators to maintain better control of the firearm.


  • Lightweight Free Floating Barrel Design
  • Steel Barrel Nut
  • Uninterrupted Upper Rail Platform
  • Integral Sling Swivel Attachment Points with Limited Travel
  • Patented Bolt-Up System
  • Mil-Spec 1913 Picatinny Rails


  • Material: Aircraft Grade 6061-T6 Aluminum
  • Finish: Military Specification Type III Hard Coat Anodized
  • Weight of Rail – 9.5 oz
  • Weight Installed – 11.2 oz (with Mounting Hardware)
  • Made in the USA!


Bolt-Up System Barrel Nut Wrench (Supplied)
Allen Wrench (Supplied)

Knights KAC Carbine M4 RAS Forend Assembly w Rib Panels

The KAC M4 RAS (Rail Adapter System) was developed for use on the US military’s M4 Carbine, and with over 1 million rails issued to date, it is one of the most battle proven designs available for the AR-15 platform. This non-free float handguard is a simple-to-install, drop-in upgrade that features genuine Mil-Spec M1913 Picatinny Rails along its entire length. What sets the M4 RAS apart from other 2-piece quad rails on the market is that it securely locks to the rifle’s barrel nut via a clamp and screw arrangement, making it a very solid foundation upon which to mount tactical accessories. Includes three KAC 11 Rib Rail Panels.


  • Length: 6.25″
  • Weight: 8.9 oz
  • Free Float: No
  • Material: Aluminum
  • Finish: Black Anodizing

Rifle Requirements: The M4 RAS is a drop-in replacement part for standard, 2-piece polymer, M4-type handguards. The rifle must have a carbine length gas system, delta ring assembly, fixed front sight/gas block, and round handguard end cap. Lighter barrel profiles work best (M4 or Government contours). Heavier barrel contours may require modification to the inside of the rail. For AR-15/SR-15 based platforms only; not compatible with SR-25 variants. Installation instructions are included.


The Super Modular Rail (SMR) MK8 M-LOK™ is Geissele’s ultra-modular model. The SMR MK8 is one of the first rails available to utilize the Magpul M-LOK technology. These rails are designed to give the user full modularity while maintaining a strong and rigid platform. Maximum venting at the lower 45° quadrants create maximum heat dissipation and also dramatically reduces the rail’s overall weight. Utilizing Magpul’s M-LOK technology at the 3, 6, and 9 o’clock positions, as well as the upper 45° quadrants. The SMR MK8 is both versatile and modular, allowing the user to tailor their platform to his or her unique needs.

The SMR MK8 also features Geissele’s proprietary 2.25″ long barrel nut. This increases the surface contact where the rail interfaces with the receiver and creates a platform that can be trusted to be straight and true the entire length of the free float rail. This increases accuracy and zero repeatability during disassembly and reassembly when performing maintenance.

Bundled with a low-profile Geissele Super Gas Block, a $59 value, the SMR MK8 is not only feature packed, but it is also value packed.


The one thing that can be agreed on is the barrels on the variations were 10.3″ inches cold hammer forged cut down from the 14.5″ inch colt m4 barrels in the early models and contracted from Colt or Daniel Defense. Were not the Colt M4A1 Heavy profile barrels. The gas ports were enlarged to .070″ and that the MOD 0 and CQBR Block 1 retained the Front Sight Block with the A frame sight. We get it, not everyone wants to spend upwards of $500 on Daniel Defense or colt Hammer forged barrels. To meet the demand and solve this problem Clint Hanson from Ballistic Advantage has begun providing these barrels for TacticalShit. They are available in limited quantity with or without FSB (Front Sight Base) and barrel nut. Which is the preferred config for building a CQBR or MK18 inspired clone.

Custom 5.56 10.3″ Hanson Government Profile Barrel w FSB and Barrel Nut by Ballistic Advantage

Looking for the perfect affordable barrel setup to complete your CQBR/MK18 Mod 0 build……’s your shit.

10.3″ 5.56 NATO Government Carbine 1/7 CrMoV barrel with pinned .750 front sight base

Includes barrel nut and handguard cap.

Custom 5.56 10.3″ Hanson Government Profile Barrel by Ballistic Advantage

Looking for that perfect barrel to start your MK18 clone inspired build…’s your shit.  The Hanson 10.3″ Gov profile barrel by Ballistic Advantage!

1 in 7 twist CrMoV

Both of these barrel options feature the .70 gas port so they will work with or without a suppressor though the true clone correct barrels were made to be shot suppressed all the time and were hammer forged produced by either Colt or Daniel Defense

Flash Hiders

The Mod0 and CQBR block 1 shared the same flash suppressor, the Knight’s M4QD flash suppressor to be mated with the M4QD Sound Suppressor. However while the the MOD 1 and CQBR Block 2 Knight’s M4QD flash suppressor/M4QD Sound Suppressor  combination they also used the Surefire SOCOM RC 4-prong flash hider and suppressor.


The advanced SureFire SureFire 3P Eliminator 556 three-prong flash hider, which fits M4/M16 weapons and variants with 1/2×28 muzzle threads, features a patent-pending design that greatly reduces muzzle flash — typically greater than 99%—when compared with a plain muzzle. Boasting robust tines built to withstand the rigors of combat, the SureFire 3P Eliminator 556 duplicates the key functional design elements of the SureFire SF3P-556-1/2-28 flash hider, but unlike the latter it cannot be used to mount SureFire SOCOM suppressors.


Early models such as the MOD 0 and CQBR block 1 retained the Front Sight Base with the A frame sight and used either a chopped carry handle rear sight, potentially Knight’s, or Matech later on. The MOD 1s and CQBR Block 2 Matech, Knight’s 300m, or other individual purchase on the rear and a Knight’s M4 folding front sight [Taupe mainly, black seen as well] for the front.


Originally designed for the US military’s SOPMOD rifle enhancement program, the KAC M4 Folding Front Sight is a low profile backup sighting solution that is designed to be attached to the top rail of a rifle’s handguard. When stowed in the folded position, the M4’s sight base extends back to envelope the front sight leaf on the right and left side, helping to protect it from damage.


KAC’s line of Micro Iron Sights are currently in use by the United States Army, Marine Corps and numerous law enforcement agencies worldwide. This is because they are built to exacting tolerances, maintain their zero under adverse conditions and, when folded, have one of the lowest profile top-rail footprints in the industry. KAC’s simple and rugged 300 Meter Folding Micro Rear Sight is no exception. More economical than the adjustable 200-600 Meter Micro Rear Sight, the fixed post aperture of the 300 Meter Micro Rear Sight is ideal for shooters who want an easy to use, close to medium range back-up sighting solution. The 300 Meter Micro Rear Sight is adjustable for windage only, and includes a snap-in polymer aperture insert that gives the user a more precise sight picture if desired.


  • Material: Steel
  • Elevation Adjustable: No
  • Windage Adjustable: Yes

Zeroing Tips: Place a target 25 meters down range and fire a 3 round group(s). Adjust the front sight post and rear sight windage knob until the desired point-of-aim/point-of-impact is achieved. If possible, place a target 300 meters down range and confirm zero.


For most of the variations 4-position carbine stock extension with Crane/LMT SOPMOD stock [1st Generation without QD swivels and newer B5 2nd Gen], CAR stock, M4 “waffle” stock, Magpul CTR/MOE, Vltor, and other stocks commonly seen with individual purchase gear. The exception being MOD 0 which used the 4-position carbine stock extension with Crane/LMT SOPMOD stock [1st Generation without QD swivels]

BCM Gunfighter Stock Assembly Mod 0


BCM Gunfighter Stock Assembly Mod 0 is made from the strongest light-weight polymer stock available for your mil-spec receiver extension is here! • Snag free Design. No sharp edges prevent tangling of the rifle with the shooter’s sling, molle gear, or other kit. • Modular VBOST (Vehicle Borne Operations Sling Tab) – This tab interfaces with the shooter’s riggers’ band or bungee to secure the shooter’s sling against the stock when the carbine is not in use. Increasingly, this is the most common application when operating inside a vehicle. • 2 different types of ambidextrous sling mounting options, including QD swivel sockets. • Integrated color matched rubber butt pad for secure shoulder placement, along with increased durability. • Simple modular design. 5 parts, and 1 screw allow for modular adaption of future stock options and configurations. • Available in Black, Flat Dark Earth, Foliage Green, and Wolf Gray.

Magpul CTR Carbine Stock

The Magpul CTR (Compact/Type Restricted) – Mil-Spec Model is a drop-in replacement buttstock for AR15/M16 carbines using mil-spec sized receiver extension tubes. Designed for light, fast action the streamlined A-frame profile avoids snagging and shields the release latch to prevent accidental activation.

The CTR also features a supplemental friction lock system that minimizes excessive stock movement for enhanced weapon stability* and an ambidextrous QD sling mount that will accept any push-button sling swivel. The Mil-Spec Model includes a standard 0.30″ thick rubber butt-pad which provides positive shoulder purchase to prevent slippage even with body armor or modular gear.

Made in U.S.A.


  • Mounts on mil-spec sized carbine receiver extension tube (not included) from manufacturers such as Colt, Armalite, S&W, LMT, and others (please see the note below)
  • Supplemental friction lock minimizes accuracy robbing wobble*
  • Sloping cheek weld combines a slim profile with user comfort
  • Shielded release latch prevents snagging and accidental operation
  • Premium chrome-silicon lock spring provides positive locking and long service life
  • Side mounting slots accept optional cheek risers for NON AR15/M4 applications
  • Removable 0.30″ Rubber Butt-Pad offers an anti-slip surface and increases impact protection
  • Compatible with Magpul ASAP®ASAP® QD and other receiver-mount sling attachments
  • Sling Mounts
    • Rear – Push-button QD swivel sling mount accommodates up to 1.5″ swivels (ambidextrous)
    • Rear/Bottom – 1.25″ sling loops
    • Toe – Lanyard hole for custom para-cord rigs

NOTE: There are two basic sizes of M4 Carbine receiver extensions (buffer tubes): mil-spec and commercial-spec. If you have a commercial-spec extension on your rifle, make sure to order the Commercial-Spec CTR.


The Magpul ACS (Adaptable Carbine/Storage) – Mil-Spec Model is a drop-in replacement buttstock for AR15/M4 carbines using mil-spec sized receiver extension tubes. Dual, rear accessible, water-resistant battery storage tubes and an integral storage compartment in the butt of the stock provides multiple storage options.

Similar to the Magpul CTR®, the ACS also features an anti-snag release latch to prevent accidental activation along with a supplemental friction lock system that minimizes excessive stock movement for enhanced weapon stability and accuracy*. The ACS comes standard with a 0.30″ thick rubber butt-pad which provides positive shoulder purchase to prevent slippage even with body armor or modular gear.

Made in U.S.A.


  • Mounts on mil-spec sized carbine receiver extension tube (not included) from manufacturers such as Colt, Armalite, S&W, LMT, and others (please see the note below)
  • Sloping cheek weld provides a wide contact surface for user comfort
  • Two water-resistant battery storage tubes located on the left and right sides of the stock
    • Each tube will store up to three CR123 lithium or two AA batteries
    • Tubes are accessible from the rear via a tethered, hand-removable rubber plug
  • Storage compartment in tail of stock with positive latching access door on right hand side
  • Supplemental friction lock minimizes accuracy robbing wobble*
  • Shielded release latch prevents snagging and accidental operation
  • Premium chrome-silicon lock spring provides positive locking and long service life
  • Replaceable 0.30″ Rubber Butt-Pad offers an anti-slip surface and increases impact protection
  • Compatible with Magpul ASAP®, ASAP® QD, and other receiver-mount sling attachments
  • Sling Mounts
    • Mid – Included reversible Sling Mount Kit – TYPE 3 fits up to 1.5″ push-button swivels (swivel not included)
    • Rear/Bottom – 1.00″ sling loop

NOTE: There are two basic sizes of M4 Carbine receiver extensions (buffer tubes): mil-spec and commercial-spec. If you have a commercial-spec extension on your rifle, make sure to order the Commercial-Spec ACS.


Yes we know. Braces are not clone correct. But if you’re waiting on your SBR paperwork or dont want to deal with jumping through hoops with the ATF just to get it done there are a couple brace options available to you so long as you dont intend to purposely shoulder your clone inspired MK18/CQBR/URGI pistol. If you intend to shoulder we strongly recommend you get your tax stamp. Two of the most popular options would be the SBA3 from sbtactical because it is a 5 position adjustable brace that is available in FDE and the strap can be swapped out for other colors. The second would be the Tailhook Mod 2 from gear head works as it is pretty damn rugged and also features some adjustment sure to make those with long or short arms comfortable.


Ever wanted a 5 Position Adjustable Arm Brace for your AR Pistol? Finally it’s possible. SB Tactical has developed a minimalist designed SBA3  arm brace that lets you choose the length of the arm brace, and keep it there. No more worry about it slipping forward while your shooting. The SBA3 Brace from SB Tactical has changed the AR15 Pistol game forever.  Approved by the BATF this pistol arm brace essentially eliminates the need for a short barreled rifle unless you intend to shoulder it all the time, in which case we strongly recommend you get your tax stamp.

Designed for all platforms capable of accepting a mil-spec carbine receiver extension, the SBA3 is 5-position adjustable, dramatically enhances versatility, and features a minimalist design with an integral, ambidextrous QD sling socket.

GearHead Works Tailhook Mod 2

Tailhook MOD 2 takes the pistol brace concept to a whole new level with it’s ability to telescope the length. The key to this is our Patented proprietary telescoping latch mechanism giving the user 5 positions of use up to a 12.75″ LOP. Combine that with the also Patented brace functionality and you have the new king of the market. The brace is injection molded out of reinforced polymer for rigidity and strength. It provides the perfect balance between size, weight, comfort and rigidity that everyone has been wishing for. A heavyweight with features all at featherweight mass, the 7 ounce (without buffer tube) Tailhook MOD 2 is the clear winner.

As with all it’s siblings, the MOD 2 uses the same fold out arm to create the support shelf that inspired the Tailhook name. This counteracts the muzzle weight of your favorite large handgun. The telescoping feature lets you find that sweet spot for balance. As an added feature, the outsides are smooth for comfortable cheeking. There is even a web sling loop.

Included in the package is the Tailhook, proprietary receiver extension, castle nut and back plate.

Remember that when this is installed on a pistol, it does not change the classification of the pistol with correct intended use.

There is always the options of buying a prebuilt upper!

The Homewrecker complete upper from Tactical Shit Skunkworks

The homewrecker” is a badass 5.56 containing only the finer things in life….or for some of you, shit that will get you divorced.  This fine piece of hardware features a Fortis upper receiver (near perfect blem) with the ultra-rare Ballistic Advantage 10.3″ 556 NATO barrel.  Fully blinged out with a 9.5″ Geissele rail in DDC, maching Airborne Charging Handle, Surefire flashhider, and lastly, to keep your rifle functioning as smooth as you hope your pending divorce will be, a Tactical Shit Nib bolt carrier group.  Does not include the EOtech as we don’t want you to be murdered by your wife. Optic not included.

Homewrecker II 10.3″ 5.56 Complete Upper by Tactical Shit Skunk Werkz Division

So we did it again with the Homewrecker II; sleeker, sexier, higher speed and lower drag. This kickass update on our VERY popular build still sports the same Fortis billet upper, but now sports all back with a Geissele 9.5″ Mk14 MLOK rail, our classic “Fuck Stick” charging handle, and the very sleek Midwest Industries flash hider impact device. Combine that with the super slick Tactical Shit Nickle Boron BCG, and the Ballistic Advantage 10.3″ barrel, this complete upper is ready for busniess!



It should be noted that while this guide isn’t fully complete we are aware of some of the parts that did not make it and we are constantly adding new inventory and will update this guide as more MK18/URG-I/CQBR related parts become available! This guide is a live document so any comments questions or concerns will be addressed within the contents of this guide as they come. We really do welcome any feedback to make this guide as accurate and complete as possible!">