When Eugene Stoner developed this rifle he did so for strictly military purposes. His aim was not to create a hunting or sporting rifle. Rather his purpose was to bring firearm design into the twenty-first century by creating fire-arms that used aircraft & man-made materials rather than wood & forged steel. By doing this he created a fire-arm that could be manufactured much more efficiently, did not require a factory outfitted with stamp & forging equipment, which is quite expensive, and could be manufactured by a number of companies rather than one devoted to producing a complex and specialized rifle.
The result was a fire-arm that, when mass produced, always weighed exactly the same, was cheaper and easier to manufacture, and weighed considerably less than the rifle it replaced. This rifle also gave the soldier who wielded it considerable fire-power and the ability to carry twice as much ammunition as before.
None of this is consistent with a sporting rifle.