An assault rifle is quite similar to an automatic rifle. However, it uses less powerful bullets than the machine gun or battle rifle. This allows the soldier using it to control the recoil of the weapon without using a bipod or something similar. Bullets like these are called "intermediate" bullets. For example, the AK-47 assault rifle often uses a 7.62x39mm bullet. The bullet is the same diameter. However, it is smaller and less powerful compared to the 7.62x54mmR. The 7.62x54mmR was what was being used with rifles when the AK-47 was brought in to service.