#.221

Today on Modern PDW Calibers we’re going to look at what might seem like a humdrum round, but which represents an important performance band for the modern personal defense weapon. That round is the 5.56x30mm MARS, a purpose built “micro assault rifle” cartridge from Colt designed to fill a similar niche to the WWII-era .30 M1 Carbine.

Anthony Williams, small arms theorist and co-author of the book Assault Rifle with Maxim Popenker, wrote an article in February of 2006 on the development of the Personal Defense Weapon and its ammunition, which he amended in late 2013. He includes in the article two photos which together represent one of the most complete collections of PDW cartridges I know of: