There are multiple factors that Cooper used to determine is a rifle is a "scout", such as:
The rifle had to be a bolt action rifle that operated smoothly. There was no particular brand or model that was preferred. Semi-automatic rifles were not prohibited, but they are difficult to meet the weight requirements.
The firearm must be under a meter in length. Today, shorter barrel rifles with 18-20 inch barrels are relatively prevalent, demonstrating Cooper's importance.
The rifle had to be 6.6 pounds, but with the sling and optics, it can weigh up to 7.7 pounds. The rifle was designed to be used across long distances, which is why a sling was included. Scout sights can help with the increased weight, but choosing the right scope for a scout rifle is critical to meeting the scout criterion.