Upgrade your AR-15 with our modular, non-proprietary system. If you are comfortable assembling an AR-15 from parts, then the installation of our War Lock™upgrade kit will be a great project for you. It is very straightforward, and our installation instructions and videos should get you going in no time.

Here you will find information that we have put together on subjects other than product owner manuals. We hope you find it highly informative and will share the knowledge with others in our community.

Options to get started

  • Buy and Install War Lock™ System yourself.
  • Buy War Lock™ System and have it professionally installed.
  • Buy installed War Lock™ System Complete Packages.


We put together the AR-15 Bolt Selection Tool, to help you determine which bolt you’ll need to run different calibers in the AR-15 platform. As you will see, there are 4 primary bolts that run the majority of the rifle calibers in the AR-15. If you own an AR-15, and installed the War Lock™ system, then adding Flexible Firepower is easy.

Bolt A is the 5.56 NATO group. You can add a complete barrel assembly from the Bolt A group and change to the ammunition for that barrel.

Want to add more flexibility? Add a different bolt group then begin selecting barrels and magazines from that group. Each new bolt group opens up new capabilities for your War Lock system.

Bolt B

Bolt B controls some of the popular “wildcat cartridges” but also includes .224 Valkyrie and 6.8 SPC. This group is great for shooters who are looking into flat-shooting cartridges and reloading/handloading their own ammunition.

Bolt C

Bolt C is easily the most diverse group of calibers controlled by one bolt. It handles cartridges from .22 caliber all the way up to .50 Beowulf, and includes 6.5 Grendel and 7.62×39 as well.

Bolt D

Bolt D controls the two most popular big-bore cartridges .450 Bushmaster, and .458 SOCOM. Looking for big game firepower out of a lighter rifle? This is your bolt group.

Bolt E

Bolt E only fires the 5.45x39mm cartridge (AK74 ammunition). A great choice for when you can find deals on surplus ammunition.


Let’s start by explaining a couple things. First is a quick picture of the anatomy making up a firearms cartridge.


The AR-15 bolt dimensions determine which calibers it can run. The two dimensions to understand are the Bolt Depth, and the Case Head Diameter.

Bolt Depth

We recommend using bolts with the same Bolt Depth (typically .124/.125″) for safety reasons.

Case Head Diameter

This dimension is the most important in determining the calibers you can run with your AR-15.  Some AR-15 bolts can run dozens of calibers, and some can only run a few.  That is mostly due to the popularity of a given cartridge.

**NOTE – Another difference between the AR-15 bolts are the extractors.  Each bolt has a slightly different extractor and/or extractor spring.  This is done to better match the extractor function to the shape of the cartridge’s case head.

Additional Considerations

Each pistol caliber listed in our AR-15 Bolt Selection Tool is based off a “blow back” bolt.  These pistol caliber bolts are weighted to the caliber (much like a handgun slide).  We recommend not using a direct impingement bolt to run pistol calibers in an AR-15.  That is because most commercially loaded (factory) ammunition creates fouling that quickly plugs the gas tube.

The Future of AR-15’s

Going through our research, we decided that the AR-15 as a Multiple Caliber platform is not only viable, it is highly beneficial.

To that end, we wanted to help simplify and standardize the multi-caliber rifle.  We started with the bolt to caliber struggle.  How do you ensure you are using the right bolt for the right caliber?  At the range?  Under stress?

A growing number of AR-15 owners are painting and coating their firearms in different colors, so we knew color coding was not going to work.

There are already a multitude of numbers associated with firearms, so number coding would just add to the confusion.

Then we had the answer.  Letter Coding the bolts and barrels.  You’ll notice in our AR-15 Bolt Selection Tool, that the bolts are grouped by letters.  A, B, C, D, E, and F (the primarily standardized rifle caliber bolts).

To further standardize and simplify the process, we removed the F bolt group.  The 7.62x39mm bolt is capable of running the two calibers that the F bolt runs.  It also allows us to run the same bolt depth across all of the bolts.  Much safer.

Bolt group E only runs 5.45x39mm, so if you don’t plan on shooting AK-74 ammunition, that leaves you 4 bolts that run all the centerfire rifle calibers for the AR-15.  Easily the large majority of possibilities, with 70+ options.

We hope you find this information to be useful, and ask that you share it with others.  By sharing knowledge with others in the firearms community, we all become better firearms owners.

Please use this information at your own risk.  Frontier Tactical can only confirm and validate the testing we performed under controlled and expert conditions.  We have no control over the mixing and matching of components found in our industry.

We work diligently to provide a safer and more compatible firearms/parts/components industry, and hope you will push for the same.

To this end, we will mark our bolts and barrels with the Letter Coding found in the AR-15 Selection Tool.

If you have any suggestions or comments, please reach out to us. Contact Us Today!

Quick Start Guide and Operating Instructions


Quick Start Guide and Operating Instructions – War Lock
Operating Instructions and Installation Manual – War Lock

FT-15 AND FTP-15

Operating Instructions and Installation Manual – FT15 and FTP15

Tools needed (not included) to install War Lock™:

  • Upper receiver action block (clamping style is recommended)
  • Workbench with a bench vise
  • AR-15 barrel wrench with torque wrench capability
  • Calibrated torque wrench
  • 5% molybdenum disulfide grease (recommended)
  • Latex or nitrile gloves
  • Applicator brush for grease
  • AR gas tube (rifle or carbine) or a # 14 twist drill (0.182 inch)
  • Thread locking compound (optional)