In combat, the difference between an enemy that is down and out of the fight versus one who is able to continue to send rounds in your direction is often measured in inches. For this reason, we should constantly strive to improve combat marksmanship. The SAC is a very powerful tool for this purpose.
Our weapon platforms and sight options typically provide a significant advantage over enemy weapons in terms of accuracy and engagement speed. Most of that advantage is lost, though, if our weapons aren’t properly zeroed.
As an example, the relative advantage in effective range that the M16A4 with an ACOG or other magnified optic has over the AK-47 loses a lot of significance if the M16 has a poor zero that causes rounds to impact 24 inches left or right of point of aim at 300 meters. Without a solid zero, our expensive rifles and optics become no better than the enemy’s AK. (In fact, our rifles may have a relative disadvantage when they aren’t tightly zeroed.) The SAC helps avoid this problem by allowing shooters to confirm zero any time: after the rifle is bumped, after taking the sight off for cleaning, during pre-combat checks, etc. We need to do everything we can, within reason, to capture every bit of the accuracy our weapons are capable of in order to ensure that we maintain the edge over our enemies. Using the SAC consistently is an important step in that direction.
Effective combat marksmanship requires more than just good equipment- it also requires training. The SAC can help you make the most of limited training time and resources. Using it saves a significant amount of time and ammunition on the zero range, each of which can be reallocated to drills on the flat range or other training. It helps to quickly identify problem weapons before those weapons create problem shooters. It also helps shooters understand the importance of consistently applying marksmanship fundamentals.