A method of supplying a rifle with cartridges includes providing classes within a group of cartridges. The classes are classified by specific and precisely graduated increments of propellant load contained in the cartridges, or by formulation of propellant, of each class relative to the cartridges of each other class. The user can test fire a rifle with multiple classes of the group and record the accuracy of the firing. A class of the group can be then chosen for a particular rifle based on accuracy of the rifle in the test firing.