Where is serial number located on lower receiver of RockRiver AR 15?

The serial number on a Rock River AR-15 lower receiver is typically located on the right side of the lower receiver, just above the trigger guard and below the magazine well. It may also be found on the rear of the receiver, near the buffer tube. The exact positioning can vary slightly depending on the model, but it is generally engraved or stamped into the metal. Always consult the manufacturer's documentation for specific details.