Caliber Conversion: Building the AR in Non-Standard Calibers

Short Story: In most cases, you can convert to or build a specific caliber of AR (within the class) by swapping out a couple of components.

Caliber-Specific Component Compatibility

EPC Calibers

Caliber Upper Receiver Muzzle Device Barrel Bolt Magazine
9mm Luger Standard Standard Standard Standard Standard
40 S&W Standard .40 Cal .40 S&W .40 S&W .40 S&W

9mm Luger

Pistol

Carbine

.40 S&W

Pistol

Carbine

AR-15 Calibers

If you are interested in learning about the AR-15 cartridges compatible with the AR-15 platform, check out THIS ARTICLE by GunDigest.

Caliber Upper Receiver Muzzle Device Barrel Gas System Bolt Magazine
5.56x45mm Standard Standard Standard Standard Standard Standard
.223 Remington Standard Standard Standard Standard Standard Standard

.223 Wylde1

 Standard Standard .223 Wylde Standard Standard Standard
.204 Ruger Standard Standard .204 Ruger Standard Standard Standard
.22 LR Standard Standard Standard

N/A2

 .22 LR BCG .22 LR
.22 Nosler Standard Standard .22 Nosler Standard Standard Standard
.224 Valkyrie Standard Standard .224 Valkyrie Standard 6.8 SPC 6.8 SPC
6.5 Grendel Standard .264 Cal 6.5 Grendel Standard 6.5 Grendel 6.5 Grendel
6.8 SPC Standard .30 Cal 6.8 SPC Standard 6.8 SPC 6.8 SPC
.300 Blackout Standard .30 Cal .300 BLK Standard Standard STD or .300 BLK
.300 Ham'r Standard .30 Cal .300 Ham'r Standard Standard .300 BLK
7.62x39mm Standard .30 Cal 7.62x39mm Standard

7.62x39mm3

 7.62x39mm
.458 SOCOM XL/Modified .458 Cal .458 SOCOM Straight Tube .458 SOCOM .458 SOCOM
  1. .223 Wylde is not a cartridge, but a chamber. It offers compatibility with both .223 Remington and 5.56x45mm cartridges, but with improved accuracy over a 5.56x45mm chamber.
  2. The .22 LR BCG is a direct blowback design and does not use the gas system for cycling.
  3. In addition to a specific 7.62x39mm bolt, you will also need an enhanced firing pin to ensure reliable ignition of the 7.62×39’s hard primers.

5.56 NATO

Pistol

Carbine

Rifle

.223 Wylde

.204 Ruger

.22 LR

.22 Nosler

.224 Valkyrie

6.5 Grendel

6.8 SPC

.300 AAC Blackout

.300 Ham’r

7.62x39mm

.458 SOCOM

AR-10 Calibers

Caliber Upper Receiver Muzzle Device Barrel Gas System Bolt Magazine
.308 Winchester Standard Standard Standard Standard Standard Standard
6.5mm Creedmoor Standard .264 Cal 6.5mm CM Standard Standard Standard
.243 Winchester Standard .264 Cal .243 Win Standard Standard Standard
.260 Remington Standard .264 Cal .260 Rem Standard Standard Standard

.308 Winchester

Carbine

Rifle

6.5mm Creedmoor

.243 Winchester

*** This requires a 15.5″ gas tube. A standard 15.1″ (rifle length) gas tube will not work with this barrel.

.260 Remington

*** This requires a 15.5″ gas tube. A standard 15.1″ (rifle length) gas tube will not work with this barrel.

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