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New 20 Round 300 Blackout Mags from Magpul: The PMAG 20 AR 300 B GEN M3

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The balance between capacity and size has been one of compromise, and Magpul's new 20 Round 300 Blackout mag fits a need many didn't know they had. Perfect for transporting a concealed SBR, or for hunters, the PMAG 20 AR 300 B Gen M3 continues in safety and reliability, distinguishing itself from mags designed for .223/5.56.

Read the Official Release:

The PMAG 20 AR 300 B GEN M3 for 300 Blackout is a purpose-built magazine for rifles chambered in 300 Blackout (300 BLK). Similar in every way to our PMAG 30 AR 300 B, the PMAG 20 is more compact for increased maneuverability and creates a more concealable package for use in small format firearms.

Since its inception, 300 BLK shooters have had to use a magazine designed for another cartridge, limiting that round’s ultimate performance and compatibility. One of the key features of 300 BLK in the past has been its compatibility with 5.56x45mm magazines. However, even with moderate success with that particular magazine, it is a compromise to do so, with reliability and safety both being at risk.

Due to the wide variety of projectile weights and profiles, and the resultant reliability issues that can come with their geometry, a dedicated 300 BLK magazine was a logical step for the PMAG line.

In addition to the performance gained by a dedicated mag, the PMAG 20 AR 300 B also offers a safer way to feed your 300 BLK rifle. When using 5.56x45mm mags, the potential to chamber and fire a 300 BLK round in a 5.56x45mm rifle with catastrophic results requires diligent ammunition management by the shooter. The PMAG 20 AR 300 B’s distinct ribbed design and smoother upper-half texture provide the shooter a distinct visual and tactile difference from any other PMAG to mitigate dangerous cross-loading issues.

Along with optimized 300 BLK performance, the PMAG 20 incorporates all of our GEN M3 features, including our next-generation impact and crush resistant polymer, aggressive front and rear texture, an easily removable slim floor plate, a paint pen dot matrix for marking and identification, and a dust/impact cover.

Blackout is a registered trademark of Advanced Armament Corp.

Made in the USA.

PMAG 20 AR 300 B GEN 3

20 Round 300 Blackout Features

  • 20 round capacity
  • Optimized for maximum reliability using 300 BLK ammunition
  • Utilizes all PMAG Gen M3 556/300B compatible accessories
  • Unique rib design to provide instant differentiation from 556 mags in all condition


  • STANAG mag well in rifles chambered in 300 Blackout

Colors: BLK
Price: $14.95


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