Yes it was- as was its predecessor the ar10, m14, fal etc. The main draw of the ar15 was the combat load increased from 140 rounds of 7.62 to 210 rounds of 5
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Ww2 fire supports came In the form of crew served 30 cal belt fed machine guns, artillery and mortars. It was slow and costly. The solution for the US and allies was to create a lightweight rifle that had similar firepower as the bar but could be serviced by a single gunner. Now a squad would have 13 rifles capable of establishing a sufficient amount of fire so other elements aka fireteam could maneuver and destroy.
Obviously most squads also have a crew served lightweight machine gun but the ar-15, or m16 are very capable at providing sufficient fires to suppress a determined enemy
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