What is the primary purpose of the bore constriction check tool for the M203?

The primary purpose of the bore constriction check tool for the M203 is to assess the barrel's internal condition. This tool is essential in determining if there are any obstructions, bulges, or other defects within the barrel that could affect the performance and safety of the weapon. Regular checks using this tool help ensure that the barrel remains in good condition and functions properly during operations. Maintaining the integrity of the barrel is crucial for the reliability and accuracy of the M203, making this assessment a key part of weapon maintenance.

The other options address different functions that are not relevant to the primary purpose of the bore constriction check tool. Measuring barrel length, cleaning the barrel, or gauging shell capacity all pertain to different aspects of weapon maintenance and functionality but do not align with the specific intent of checking for internal damage or obstructions.