How should you conduct the micrometer test on the M1A1 Gunner's quadrant?

The micrometer test on the M1A1 Gunner's quadrant requires that the micrometer knob be set to 0 as a critical step to ensure accuracy in measurements. By setting the micrometer knob to 0, you establish a reference point for the test, which is vital for assessing the proper functioning of the quadrant.

This calibration ensures that any subsequent measurements taken will be based on a known standard, thereby allowing for precise adjustments to be made. Cleaning the shoes prior to conducting the test is also essential, as it helps to eliminate any debris that could interfere with the measurement or functionality of the quadrant, ensuring an accurate and effective test.

In contrast, selecting a different setting, like 5, would create an incorrect baseline for the test and could lead to errors in measuring the quadrant's performance. Setting the tube to 90 degrees is unrelated to the micrometer testing procedure and does not directly impact the measurement accuracy required for the test.