This is the larger version of the XM-15S carbine only chambered in the long range 308 Winchester cartridge. It has the standard flattop upper receiver, with the permanently attached tubular aluminum hand guard and standard gas-impingement operating system. It has the long 24 inch heavy stainless steel target grade barrel with the low profile, gas block with the Picatinny rails on top. Fitted with the standard M16A2 style plastic buttstock with the butt trap compartment and a black plastic pistol grip. The lower receiver has the standard factory address and model markings with the "SAFE/FIRE" markings on each side. It is complete with one 20 round factory magazine.