Mk12 SPR 18" barrel kit for Mod 0 and Mod 1 rifles

$465.00 - $806.00
generally in-stock, and will ship in 2 to 4 weeks, allowing for coating. In rare event that we are waiting on barrel shop, we will place in backorder status
AEM Collar Selection:
in comments mention SHORT or LONG, or we default to first available.

Mk12 SPR 18" barrel kit for Mod 0 and Mod 1 rifles - with Ops Inc. / AEM hardware ready to install


Ready to install barrel, Ops, Inc. brake and collar

Let's face it.  When we are building a Mk12 we want everything just right.  Charlie's is here to help. Here is our short list of barrels that will work wonders for you, already coated to spec, and we have included the Mk12 barrel and the Allen Engineering long or short collar, brake and thread protector.  You benefit from our research, our testing, and clone ready barrel.

Just add this setup to your clone receiver setup, or if you are looking for a specialty Mk12 inspired look, have at it. Oh, you might also need the right handguard, optic, stock, bipod and rings.  

We have done the research.  We have purchased a number of popular barrels and put them through the test to see if we could fit the Ops, Inc or Allen Engineering collar and brake on the barrel, and then attach the AEM-5 / Ops Inc. #12 suppressor on the barrel with collar and brake setup.


We can cut to the chase.  All the barrels would accept the Mk12 gas block from either Daniel Defense or Badger Ordnance.  Some took some effort, some allowed the gas block to slide right on.  All would accept the Allen Engineering long or short collar and the brake with shims But several were out of spec to accept the Allen Engineering AEM-5 suppressor.  Charlies does really understand why.  Ron Allen has supplied the SPR profile to any barrel maker who chooses to follow.  Several brands were not in spec.  Generally, this means that the measurement of the end of the threads to the shelf point where the collar attaches was not the correct distance.  Now, in talking to Ron Allen, he explained that he has been seeing a number of baffle strikes in his suppressor, but upon further research, the problem was one of two things:  1)  some rifle manufacturers were having the Ops Inc collars and brakes make by another vendor, or maybe they were making the brakes and collars themselves, but Ron tells us that they were not in spec, and were not Allen Engineering products.  2)  the profile of the barrel was not to spec, and generally, the distance from the muzzle to the collar step was too short.  This results in the suppressor making two few turns, and the alignment against the collar is not quite right, or to make it right resulting in far too much shimming and far too little of the barrel thread actually inside the suppressor.

To get the suppressor of a Mk12 / Ops Inc / AEM-5 aligned properly is a very delicate and technical task.  The suppressor rests on on the collar, but then is threaded inside the suppressor onto the external threads on the brake.  There is a certain number of turns that are needed for all this magic to happen and the suppressor to perfectly rest on the collar, and be securely fastened to the threads on the brake.

So, Charlies brings you the short list of barrels that perfectly fit.

If you do not need a suppressor, don't sweat it.  Many barrels will fit the gas block and the Allen collar and brake.  For most people, that is good enough.  Also, there are some rifle and barrel brands out there that are not trying to be clone correct.  In fact, one of them tells you that they have found the better secret sauce and improved upon the original Mk12 design.  They are probably correct.  After all, the Mk12 made its way into the battlefield in 2001, so that is a long time ago, and there are better rifles and better barrels out there than the 18" SPR barrel. 






If you want to build your Mk12 to be historically, correct, then we are your huckleberry.  We have shortlisted four barrels, with hardware and gray or black coating ready to go.  Charlies is offering three different barrels

Barrel Selection

  • Douglas 1:7 twist Stainless Steel barrel, 18.1" in traditional gray, and custom chambered and profiled by Compass Lake Engineering, then custom coated with GunKote by Potomac Armory.  This is for the purist.  This is 100% clone correct.  If you are looking for perfection, this is your barrel.  Charlies has spent time at Frank's shop at Compass Lake.  These guys do magic with barrels, and Frank noted that the 18" barrel has caused issues over the years with excessive gas port erosion, but he has not seen that with Douglas.  You might not know Douglas for barrels, but if you are looking for perfection in your Mk12 build, you will want Douglas, and you will want the craftsmanship that Charlies brings you with Dougas, Allen Engineering, Potomac Armory and traditional gray GunKote, all in one package.
  • Criterion 1:7 twist Stainless Steel barrel, 18.0" in black, and custom chambered and profiled by Craddok Precision, then custom Cerakoted in black by Potomac Armory.  Charlie's has learned barrels, especially partnering with the barrel engineers at Potomac Armory.  Charlies and Potomac have done some great barrel design and build with Criterion.  The family that owns Criterion studied under Boots Obermeyer, the master barrel smith of the 20th Century.  So did Krieger and a few other names you would know.  Charlies gets more and more impressed with the innovation, quality and customer service at Criterion, and while it is a button broached barrel, and not rifle cut, their technology has gotten to be so good, it almost does not matter.  Paul Craddock is part of the next generation of great barrel smiths, and we have chosen Craddock because of their attention to detail, their ability to scale quickly, and the fact that we need to support the next generation of great craftsmen in barrel work, and also Paul and Ron Allen have a clear understanding of what works with Mk12 profiling.  The Criterion barrel is an amazingly good choice, and comes in just a smidge less money than the Douglas.
  • Bergara 1:8 twist Stainless Steel barrel, 18.0" in traditional gray.  (No longer available)
  • Bergara 1:8 twist Stainless Steel barrel, 18.0" in black.  (No longer available)
  • Bergara 1:8 twist Stainless Steel barrel, 18.0" in FDE.  (No longer available)
  • Bergara 1:9 twist Stainless Steel barrel, 18.0" in traditional gray.  This is a 5.56 NATO chambered barrel from Bergara and then custom coated in Cerakote Potomac Gray.  Here, you are getting 1:9 twist, so not 100% clone correct, but the 1:9 twist will be excellent for use with M193 5.56 NATO 55 grain ammo, which is quite a bit more available and affordable than the 77 grain (which was designed for the 1:7 twist).  Charlies has tested the fit, and it is just as good as Douglas or Criterion for the AEM-5 suppressor.




One note:  there are a number of super great quality companies who are making barrels and uppers and rifles that are Mk12 or Mk12 inspired.  Many of which, we have tested, and there are some we have not.  You should not take away that if that barrel is not listed that it failed our testing.  Some did.  There are probably barrels, other than what we have listed that will work just fine.  As we test more, we may choose to offer more.  At the end of the day, we are looking for quality and adherence to the specifications that AE has given.  We are comfortable with the four barrels we have listed, and stand by them.  You might like another barrel.  No hard feelings.  We cannot sample everything, but we feel that we sampled enough of what is on the market to make some strong endorsements for the barrels listed.  Could we give you three more barrels that will work just fine?  Maybe, but this is a good start.

What we have listed will fit the bill for Mod0 or Mod1 builds.  We have not yet addressed the Mod H or the NSW Recce.  That will be another topic.  The latter two versions have shorter barrels.

Enjoy with confidence.

Specifications:  each kit contains:

  • An SPR profiled barrel suitable for a Mod0 or Mod1 build, with an M4 barrel extension, drilled gas port and crowned and threaded muzzle at 1/2"-28 threads.
  • Your choice of an AEM collar and brake kit in short or long.  Short is needed for Mod0, but short or long can be used for Mod1, ModH, or NSW RECCE builds.
  • Inspected and packaged in milspec (blue) anticorrosive VCI plastic tubing by Charlies Custom Clones.
  • 30-day money back guarantee.  Since we are sponsoring this.  If you are not happy, and have not shot it, return it for a full money back refund.
  • No gas block is included.  The kit is unassembled, as you will need to insert the barrel nut, for the handguard or rail of your choice.  We wanted to do it all, but the fact is you need to get the barrel nut on first, and then the gas block, and the gas block will vary, based upon the model you are building:  Mod1 or Mod0. 
  • Instructions are very detailed as to how to time the Allen brake.


If you are building a Mod 0, you will want to need the PRI Gen1 flip-up sights with the cross-bolt installation.

If you are building a Mod 1, you will need A Mk12 gas block, ready for you to install, either the Potomac Mk12 gas block or the Badger Ordnance Mk12 gas block or Daniel Defens Mk12 gas block.

Note:  One picture shows the Mk12 gas block installed.  The gas blocks are available for purchase, but not included in the base price, as Mk12 gas block is only correct for the Mod 1.

Charlie's also offers installation of the complete kit with the gas block and your barrel nut, or the entire upper receiver with your rail for an additional feeNote that to assemble the barrel kit, we will need the barrel nut that you will be using, or you will need to buy the barrel nut from us.  The barrel nut must be installed before the installation of the gas block and the collar and brake.  The barrel nut is also include in the PRI or KAC rail for the Mod 0 and Mod 1 respectively.  Most customers will choose to purchase the rail with the barrel if Charlie's is installing the kit, but if you have a rail, you can send us the barrel nut separately.

  • For the Mod 0, we will install the PRI folding gas block and time the cross bolt pins, and use a thread locker on the screws, but you will still be able to remove or adjust the hex head screws, which was often used by snipers to adjust for windage.  The collar will be properly installed, and the brake will be timed and set in place with rockset.  The service fee for the Mod 0 is $100, and you can add that here, and let us know the reason for adding shop service in the comments when you check-out.
  • For the Mod 1, we will install the Mk12 gas block first by dimpling the barrel, then timing and setting the gas block and installing the set screws and applying red Loctite.  This is considered a semi-permanent installation.  It is possible to remove the gas block, but often times the removal requires the drilling out of the set screws and sometimes destroying the gas block threads in the process.  The collar will be properly installed, and the brake will be timed and set in place with rockset.  The service fee for the Mod 0 is $110, and you can add that here, and let us know the reason for adding shop service in the comments when you check-out.


Note on availability and pricing

On pricing, some barrel kits might seem high, but keep in mind, you are getting the gas block, and the AEM muzzle kit, the barrel coating and Charlie's selection and handling, all in one place.  We have invested a lot of time and inventory and research into Mk12 barrels.  You can count on getting the right barrel.  On delivery timing, some barrels are in stock, and others need to be made, not to order, but in batches, and also tested and coated, so plan on a good 5 weeks for your barrel delivery.  Some will ship in 1 or 2 weeks, some in 5 to 8 weeks.