An insensitive munitions (IM) primer for use with major caliber gun systems, including an elongate housing, a tube, an ignition assembly, and a booster assembly. The elongate housing has a proximal end and a distal end. The tube has a first end coupled within the distal end of the elongate housing. The ignition assembly is located within the proximal end of the housing. The booster assembly is located within the elongate housing adjacent the ignition assembly and including a booster holder providing a cylindrical structure defining an internal bore in which a first burst disk resides and is mechanically restrained by a booster disk lock.