A firearm receiver assembly includes a receiver body, a threaded mount at a rear portion of the receiver body, a magazine release assembly including a magazine release portion on at least one side of the receiver body, a bolt release assembly including a bolt release central portion and a bolt release portion on at least one side of the receiver body, and a safety selector assembly including a safety portion on at least one side of the receiver body. The bolt release central portion translates vertically within a cavity of the receiver body.