I'm just having a debate with a friend in my fleet as to which is more powerful, I've noticed more damage on Volley 3 over RF 3? However I'd prefer hard facts to speculation?

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Up until recently Scatter Volley contained a glitch which cause it to deliver more damage than intended when used on a single target compared to Cannon Rapid Fire. A patch was added which corrected this and as of current they do about the same with cannon rapid fire three delivering slightly more damage than cannon scatter volley three. Though I cannot remember when this patch occurred exactly I believe it was at least as of season 2's release.