They're right -- accuracy is potential. It is the sum of the weapon, the ammunition, and the shooter. As an old gunnery instructor of mine was wont to say, "Gunnery is an exercise in probabilities." In other words, a given system (gun, ammunition and shooter) can place their shots in a circle of a certain diameter at a given range. The more accurate the system, the smaller the circle. Hitting what you aim at is a matter of centering the circle on the point of aim.