Which procedure is particularly risky when modifying the Howa HACT trigger?

Cutting back a spring is particularly risky when modifying the Howa HACT trigger because it directly impacts the function and reliability of the trigger mechanism. The spring is a critical component that dictates the weight of the trigger pull and how the trigger resets. If the spring is cut too short, it can lead to a light or unintended trigger pull, which increases the risk of accidental discharges. Additionally, modifying springs can lead to unpredictable results, making it difficult to ensure consistent performance or safety.

In contrast, replacing screws may involve alteration but does not inherently affect the trigger's operational integrity if done correctly. Cleaning the trigger housing is a routine maintenance procedure that enhances performance and does not introduce risk if done properly. Adjusting the stock fit relates to the overall ergonomics of the rifle rather than the trigger mechanism itself and is less likely to influence trigger performance directly.