Palmetto State Armory PA-15 .300 Blackout
Model: 516444735
Palmetto State Armory PA-15 .300 Blackout
Model: 516444735
Full Specifications
About This Firearm
PSA's PA-15 in .300 Blackout is the commodity floor of this caliber — a forged 7075-T6 AR-15 with a Carpenter 158 bolt, nitride-finished 4140 barrel, and Magpul furniture throughout. PSA's pitch is straightforward: the PA-15 .300 BLK uses the same forged lower as their 5.56 rifles, with only the upper changed for the caliber. That means most owners already know this lower intimately, and upgrades, spare parts, and institutional knowledge transfer directly. The Magpul MBUS flip-up sights included in the box put it ahead of the DDM4 V7 on out-of-box shootability without adding cost.
The shared lower with PSA's 5.56 rifles is a feature and a responsibility: it's easy to swap uppers, which means you need disciplined magazine labeling to avoid chambering a .300 BLK round in a 5.56 upper — a combination that will destroy the gun. The pistol-length gas system and 16" barrel run supersonic loads without issue; for heavy subsonic loads suppressed, owners report the PA-15 benefits from a heavier buffer or adjustable gas block, which neither the DDM4 nor the CMMG Dissent require.
Best For
Strengths & Limitations
- The lowest-cost entry into the .300 BLK AR-15 platform with a Carpenter 158 bolt, forged 7075-T6 receivers, and Magpul MBUS backup sights already included — components that would otherwise be add-on costs on comparable budget builds.
- Standard AR-15 lower means every holster, case, part, and upgrade designed for a mil-spec AR fits without modification. Owners who already run a PSA 5.56 lower share the same magazine well, trigger group, and furniture across both rifles.
- The pistol-length gas system is a trade-off at 16". Owners report that subsonic 220gr loads run unreliably suppressed without a heavier buffer (H2 or H3) or an adjustable gas block — both of which cost extra and add setup time the CMMG Dissent avoids by design.
- The PSA lower is identical to their 5.56 PA-15. If you own both, you can inadvertently swap uppers and load a .300 BLK magazine into a 5.56 upper. A .300 BLK round chambers in a 5.56 barrel and will destroy the gun if fired. Mark your .300 BLK mags clearly before this rifle leaves the box.
- No chrome lining in the chamber or bore. The nitride finish is adequate for most use, but owners who shoot heavy subsonic loads at high round counts report faster chamber wear than chrome-lined alternatives like the DDM4 V7.
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Frequently Asked Questions
Why is magazine discipline more critical on the PA-15 than on other .300 BLK rifles?
The PA-15's lower receiver is the same forged unit PSA uses across its 5.56 lineup, which means a 5.56 upper drops onto this lower with zero modification. If you own both a .300 BLK and a 5.56 PSA, the uppers are interchangeable on the same lower — and that's the failure mode to design around. Mark every .300 BLK magazine with bright tape (orange or red electrical tape around the baseplate works well), a permanent marker stripe, or labeled mag sleeves. Store them in a separate bag or box from your 5.56 mags. Some owners use a different magazine brand entirely for their .300 BLK loads so the profile is visually distinct at a glance. The risk is lower on platforms with non-interchangeable lowers (CMMG Dissent), but on a PSA it's a daily-discipline issue.
Will the PA-15 cycle subsonic .300 BLK loads reliably?
Unsuppressed, most 220gr subsonic loads cycle the PA-15 without issue. Suppressed, the added back-pressure from a can often over-gases the pistol-length system with heavy subsonics, causing bolt bounce or double-feeds. The fix owners use most often is an H2 carbine buffer or an adjustable gas block. Neither is difficult to install, but it's an extra step that purpose-built subsonic platforms like the CMMG Dissent don't require. If suppressed subsonic use is the primary plan, budget for one of these upgrades at purchase.
