To get 100% effectiveness go to gen1, find an Astro and kit it to land, right before it runs into you out a behemoth gate and the door for it between you and it so it runs into it, then pop out a mek with the siege cannon module and shoot the top of its head and there you go 100% effectiveness Astro at the cheap price of of a behemoth, mek, M.C.S.M (siege cannon, and some cannon shells