periodicAction
actionCountType "Infinite"
actionIntervalTime
Level:0 2.500000
Level:1 0.000000
Level:2 0.000000
Level:3 0.000000
buffInstantActionType "ApplyBuffToTargetsAtOrbitBody"
instantActionTriggerType "AlwaysPerform"
If you enter the grav well, you get the buff.
seems that if you leave, you still keep the buff, as the finish conditions are:
finishCondition
finishConditionType "LastSpawnerNoLongerHasBuff"
buffTypeToQuery "BuffCannonShellPsi"
SO, in theory, you could get your fleet ready to jump, use the cannon on your own planet, and jump right when it hits, so that you get most of the 25% bonus, without hte timing issues. Prolly fire a second bolt at the planet you are attacking when your fleet arrives.