Calvin several vendors advertise this drum as .223/300 BO compatible. This was C&P from X Products web site, describing this drum magazine: "Our AR-15 High Capacity Magazines designed for .223 / 5.56 and 300 Blackout rifles are primarily constructed from aluminum with minimal plastic parts, feature a Cerakote™ finish, and DO NOT require lubrication to operate (NO LUBE REQUIRED). High capacity magazines for AR-15 .223 /5.56×45 , 9MM, 300 BLK, .308 / 7.62×51. High-quality magazines with 50 round capacity." So, yes, it is 300 BO compatible. No need to call X products - I did the research for ya! Have a good one!

Calvin, I would talk with X-Products. They say this will work with most 300blk then say a variant of this magazine would work. They can answer definitively at 928.852.0078 ------- xproducts.com/product/x-15-50-round-ar-15-high-capacity-magazine/