The .300, .338, .375 family of Remington American Magnums was designed by Aleksandr Kolesnikov of Houston, Texas, USA in February 2010. This was a response to the .375 Ruger. It is based upon the .300 RUM case, shortened to 2.580" to fit into Standard length Remington 700 action (firearm), while maximizing powder capacity by using .550" case diameter instead of Ruger's .532".