Which is the factor of weapon's ability to suppress

[tokiedian]

Studying tactics of WinSPWW2, I focused on which unit is good at supporting. I made the list of german weapon's Kill.

Then, I found Kill of 7.5cm KwK37, which is the main gun of PzKw IV, is smaller than one of LMG and the same value as one of SMG. It seems too powerless to use as a support weapon, although PzKw IV was made for close support tank. Therefore I thought there are other factors of weapon ability to suppressing. I guess Warhead would be one of them, although MG's warhead is 1. Which is the factor of weapon's ability to suppress?