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 |
- .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.
- The .22 LR BCG is a direct blowback design and does not use the gas system for cycling. If your gun is equipped with an adjustable gas block, we recommend closing the gas system to prevent unnecessary fouling from the rimfire ammunition.
- 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
.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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