What is the most critical factor when aiming for extreme accuracy in ammunition?

When aiming for extreme accuracy in ammunition, proper case run out is recognized as a critical factor because it directly influences the alignment of the bullet as it is seated in the cartridge and subsequently fired. Case run out refers to the degree to which the case is out of round or not perfectly aligned with the rifle's chamber. If the case is not uniformly aligned, it can lead to inconsistent bullet travel and ultimately affect the bullet's trajectory and accuracy.

When a bullet is fired, any misalignment can cause it to exit the barrel in a less-than-ideal manner, leading to variations in its path. This inconsistency can manifest as a spread of impacts on the target, reducing the overall precision of the shooting. Maintaining a low run out improves concentricity, resulting in a more stable bullet flight, which is paramount for achieving extreme accuracy.

The other factors mentioned, while important, are generally considered to have a secondary impact on accuracy compared to case run out. Consistency in powder selection, correct bullet seating depth, and uniform primer ignition all contribute to performance, but if the case alignment is compromised, those improvements may not achieve their full potential. Therefore, prioritizing the control of case run out is essential for achieving the utmost accuracy in ammunition reloading.