Resolute is Rifle AR-15 purpose-built, high-quality solution for those who simply cannot settle for second best. The Resolute has been crafted for precision, control, and ease of use. A billet 6061 T6 upper receiver assembly is available on the Resolute 100. This.Rifle AR-15 RESOLUTE Upper Group is a great choice if you want to build an Rifle AR-15 for plinking, training, or hunting small game. The Mk4.22 LR upper is compatible with all Rifle AR-15 lowers and CMMG.22 Conversion Magazines.