[Windows]

looks somewhat like a gimmick to me. It seems like the kit is working against itself by increasing the spring tension. As a general rule, an increase in spring tension will decrease felt recoil. This is applicable on airsoft and real guns alike.

The weights should help because E=mv^2 and I=mv. therefore, if E is constant, an increase in M should cause a decrease in V and an increase in I. If you want the most felt recoil,you should use a heavy bolt+carrier and the lightest spring that still returns the bolt to battery. You could also increase the E in the equation by using a stronger gas, or use high flow valves.

Hope this helps.