The cartridge was developed to provide improved performance from the AR platform with only a barrel change, using standard magazines, bolts, and gas impingement systems.
The design parameters of the 300 BLK make it the ideal round for shorter barrels (where the 5.56x45mm is especially lacking) and for suppressed applications. Supersonic loads provide ballistic performance on par with the 7.62x39mm, while subsonic loads vastly outperform the 9mm Luger for suppressed applications.
Although the 300 BLK was developed around standard AR/M4 magazines, they were designed for the 5.56x45mm, limiting performance and compatibility.
While some 300 BLK rounds function reliably in 5.56mm magazines, others don’t interface correctly with the contact areas of the magazine. Dust and fouling from blowback exacerbate the problem, especially with some of the subsonic and monolithic-bullet rounds, creating side-pressure-induced friction, slowing stack movement.
Given the wide variety of projectile weights and shapes potentially decreasing overall reliability, a dedicated 300 BLK magazine designed specifically for the cartridge is needed.
With the popularity of the 300 BLK, a dedicated PMAG® for the cartridge was a logical step for Magpul®. The new, patent-pending Magpul PMAG 30 AR 300 B GEN M3 is a dedicated, purpose-built magazine for AR-pattern rifles chambered in 300 BLK. It has a 30-round capacity and features an optimized internal geometry that accommodates the wide variety of bullet profiles used in 300 BLK cartridges.
If you chamber a 300 BLK round in a 5.56mm gun, it can go into battery by pushing the bullet back into the cartridge case. Firing the round will have catastrophic consequences. The easily identified rib pattern of the PMAG 30 AR 300 B GEN M3 helps avoid this mistake.
The PMAG 30 AR 300 B GEN M3 has all the great features of the GEN M3 line, including Magpul’s next-generation impact- and crush-resistant polymer, aggressive front and rear texture, an easily removable slim floorplate, a paint pen dot matrix for marking and identification, over-travel insertion stop, and a dust/impact cover.
All of the GEN M3 line feature lower profile ribs than previous generations. The slightly slimmer profile provides better compatibility with tight double and triple magazine pouches.
All Magpul PMAG GEN M3 accessories work with the PMAG 30 AR 300 B GEN M3, including the MagLink® , Ranger Plate™, Original Magpul®, Minus Five-Round Limiter, and Minus Ten-Round Limiter. The Round Limiters are intended for temporary capacity reduction and do not make a banned magazine legal.
Magpul is a perfectionist when it comes to its products. The PMAG 30 AR 300 B GEN M3 underwent a lengthy development and testing process before going into commercial production.
Hornady® LE provided 200 rounds of 110-grain GMX® TAP® 300 BLK for my evaluation. I have also tested the magazines with Hornady 125-grain HP American Gunner® and Black Hills 220-grain OTM.
The 110-grain GMX TAP is designed to provide barrier-blind performance and meet FBI Ammunition Test Protocols. The polymer-tip monolithic copper alloy bullet is designed to deliver controlled expansion, with 95+% weight retention.
The streamlined design of the GMX projectile (.305 BC for the .308 110-grain GMX) provides an ultra-flat trajectory. The lead-free gilding metal construction reduces the pressure and fouling associated with pure copper bullets.
A custom San Tan Tactical STT-15 300 BLK pistol was employed as the test platform for my evaluation, along with a Blue Force Gear® Ten-Speed® M4 Chest Rig, an ultra-light, ultra-low-profile chest rig that holds four M4 magazines. The Ten-Speed pouches utilize military-grade elastic combined with ULTRAcomp® high-performance laminate.
The multi-use pouches are hydrophobic, lie flat when not in use, and weigh practically nothing. It’s an ideal bail-out rig. For those with the need, it’s easily concealed under the right cover garment.
The performance of the PMAG 30 AR 300 B GEN M3 has been flawless. They’re outstanding magazines. The PMAG 30 AR 300 B GEN M3, 300 BLK has a suggested retail price of $15.95. As of this writing, it’s available in black only.
MAGPUL INDUSTRIES, INC.
BLACK HILLS AMMUNITION
BLUE FORCE GEAR
HORNADY MFG. CO.
SAN TAN TACTICAL