300 Blackout AR-15 build
300 Blackout gives an AR-15 a .30-caliber bullet while keeping the same lower, bolt carrier group and magazines as 5.56: only the barrel changes. This build uses a 16-inch barrel, so it's a regular rifle with no NFA paperwork (a shorter barrel makes it a short-barreled rifle or an AR pistol, with their own rules), a pistol-length gas system that suits 300 Blackout, a lightweight M-LOK handguard and a red dot.
Mark your magazines: a 300 Blackout round can chamber in a 5.56 rifle, which is dangerous. Prices update every night from the stores we track.
Total today
$632.74
6 parts · lowest price at the stores we track · updated Oct 4, 2026
Our compatibility checker found no problems.
Parts list
| Part | Pick | Price |
|---|---|---|
| Lower receiver | PSA AR-15 Complete Lower Magpul MOE Edition - Black, No Magazine - 5165447832Complete lower with a Magpul MOE stock and grip; any mil-spec AR-15 lower runs 300 Blackout. | $129.99Palmetto State Armory Sale |
| Upper receiver | PSA 16" Pistol-Length 300AAC Blackout Nitride 13" Lightweight Hex M-LOK Upper - No BCG or CHPalmetto State Armory16-inch 300 Blackout barrel, pistol-length gas, 13-inch M-LOK handguard; sold without a bolt carrier group or charging handle. | $249.99Palmetto State Armory |
| Bolt carrier group | PSA 5.56 Phosphate MPI Full-Auto Bolt Carrier GroupPalmetto State ArmoryA standard 5.56 bolt carrier group runs 300 Blackout: the bolt face is the same. | $99.99Palmetto State Armory |
| Charging handle | AR-15 .223 Charging HandleLuth-ARMil-spec charging handle. | $18.79BrownellsIn stock |
| Optic | Romeo5 Gen II Compact 1x20mm 2 MOA Red Dot BlackSig SauerRed dot with a 2 MOA dot; fast with supersonic or subsonic ammo. | $119.99BrownellsIn stock Sale |
| Magazine | Magpul 30 Round PMAG GEN M3 - BlackMagpul5.56 PMAGs feed most 300 Blackout loads; heavy subsonic rounds can feed better from 300 Blackout magazines. | $13.99GunMag WarehouseIn stock |
Prices and stock can change at the store after our nightly check. MyGunLab earns a commission when you buy through store links, at no extra cost to you (disclosure). Background: our guide.