Advanced Armament Corporation MPW rifles with 16" barrels(300 AAC BLACKOUT). A 30 caliber rifle the size of an AR 15 5.56mm caliber rifle- without a reduction in magazine capacity. The AAC MPW in 300 AAC Blackout uses ordinary 223/ 5.56mm magazines! The package includes a Magpul PMag 30 Magazine.

What? Never heard about 300 BLK? Check this link http://en.wikipedia.org/wiki/300_AAC_Blackout_%287.62%C3%9735mm%29