With every gun manufacturer on the planet working to improve the stg-44 , the allied forces were arguing about which cartridge to chamber in the FAL . Belgium licensed almost every free world country to manufacture their own . The Spaniards went with the cetme , and the Germans improved it to the HK G-3 , all chambered to the US .308 , renamed to its metric equivalent. History isn’t too clear on why the U.S. didn’t follow suit with the FAL or the L1A1 . Some say the weight of the rifle , expense of both manufacturing the rifle and ammunition. Many in the pentagon liked the power of the .308 , and this is where the stories get cloudier . It seems that some in the pentagon had way too much cash and time to shop around . One might think they were shopping for kickbacks , dragging their feet and unofficially arguing about the AR10 and then it’s scaled down copy the AR15, later the M16 . Much cheaper to shoot and less recoil with the straight bolt carrier design .