Close
800.992.3771 info@frontiertactical.com
AR-15 Caliber Quick Reference Guide

AR-15 Caliber Quick Reference Guide

AR-15 Caliber Quick Reference Guide

This AR-15 Caliber Quick Reference Guide should not be considered as a comprehensive, exhaustive list for caliber changes. Frontier Tactical™ created this list to quickly assist the AR-15 owner in the requirements necessary for switching calibers using the War Lock™ Multiple Caliber System. This list only includes cartridges that currently have commonly available components. We are constantly researching and improving our list as new products, technology and information is made available.

Calibers requiring a barrel change only

(using a standard mil-spec, 5.56 NATO, AR-15)

.17 Remington .17-223 .20 Practical .204 Ruger
.25-45 Sharps 5.56x45mm NATO/.223 Remington 6x45mm .300 AAC Blackout

Calibers requiring no barrel change if used with a conversion kit

(using a standard mil-spec, 5.56 NATO, AR-15)

.22 LR (conversion kit is commonly supplied with one magazine)

Calibers requiring a barrel, bolt and magazine change

(using a standard mil-spec, 5.56 NATO, AR-15)

5.45x39mm (5.45x39mm bolt, barrel and magazine) 6.5mm Grendel (6.5mm bolt, barrel and 6.5mm/5.56mm NATO magazine) 6.8mm Remington SPC II (6.8mm Rem. SPC II bolt, barrel and magazine)
7.62x39mm (7.62x39mm bolt, barrel and magazine) .243 LBC (.243 LBC bolt, barrel and 6.5mm/5.56mm NATO magazine) .264 LBC (.264 LBC barrel, 6.5mm/.264 LBC bolt and 6.5/5.56mm NATO magazine)
NOTE – Our BHW .264 LBC barrels are “Type I” (bolt depth of .125″), and use a common 7.62x39mm bolt to fire .264 LBC or 6.5mm Grendel. American 30 BHW (American 30 BHW barrel, 6.8 Rem. SPC II bolt and magazine)

Calibers requiring a barrel, bolt, modified upper receiver and magazine change

(using a standard mil-spec 5.56 NATO AR-15):

.450 Bushmaster (.450 Bushmaster barrel, bolt, magazine and modified upper) .458 SOCOM (.458 SOCOM barrel, bolt, 5.56 NATO magazine and modified upper) .50 Beowulf/12.7x42mm (.50 Beowulf/12.7x42mm barrel, bolt, magazine and modified upper)
NOTE – All of our upper receivers come with an enlarged ejection port to accommodate calibers up to, and including .50 Beowulf.

Some AR-15 calibers can be purchased ONLY as complete uppers from a multitude of other companies. These calibers do not have a common source for the components (typically the barrel, bolt and magazine) that an AR-15 owner needs to build that caliber barrel for themselves

For this reason, the calibers requiring the purchase of a complete dedicated upper receiver are not listed in our quick reference. They do not meet this list’s requirements for having enough currently available components to support the common use of this cartridge through the AR-15 platform with an owner building their own multiple caliber system. That should not discourage the AR-15 owner from considering any of the calibers not listed here.

Please reference our Comprehensive AR-15 Caliber Reference for all options available for the AR-15 platform. This guide also includes direct sources for the components necessary to build your own multiple caliber AR-15.

We hope this AR-15 Caliber Quick Reference Guide was helpful. Our goal was to provide a user’s quick reference for anyone who wondered what changes or conversions are necessary to fire specific caliber cartridges through an AR-15.

Leave us a comment below!