The entire point of 300 AAC Blackout is that you don’t need to change any of your existing gear. The cartridge fits in existing AR-15 magazines, the barrels fit into existing AR-15 upper receivers, and the bolts are the same bolts you’d get with any 5.56 NATO rifle. But Magpul has gone ahead and made a version of their PMAG specifically for the 300 BLK cartridge. Here’s what they have to say about it.
The PMAG 30 AR 300 B GEN M3 is a purpose-designed magazine for rifles chambered in 300 Blackout. Since its inception, 300 Blackout shooters have had to use a magazine designed for another cartridge, limiting its performance and compatibility. One of the nice features of 300 Blackout is the compatibility with 5.56x45mm parts, but with the magazine it is a compromise to do so. Due to the wide variety of projectile weights and shapes potentially decreasing overall reliability, a dedicated 300 Blackout magazine was a logical step for the PMAG line.
In addition to the performance gained by a dedicated mag, the PMAG 30 AR 300 B also offers a safer way to feed your 300 BLK rifle. When using 5.56 mags, the potential to chamber and fire a 300 BLK round in a 5.56 rifle with catastrophic results requires diligent ammunition management by the shooter. The PMAG 30 AR 300 B’s distinct rib design provides 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 30 AR 300 B brings along all of the GEN M3 features such as 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.
Dedicated, purpose-designed magazine for rifles chambered in 300 Blackout
Optimized internal geometry accommodates the wide variety of bullet profiles used in 300 Blackout cartridge
Distinct rib design provides the shooter a visual & tactile difference from any other pmag to mitigate dangerous cross-loading
Carries forward the physical & performance features of the rest of the gen m3 line
MSRP is about $15.95.