All right, I've been wondering about this since I first saw the way that they show stats for synergies.
Say you have a shottie with Brutal synergy:
[1]+5% Melee Dmg
[2]+10% Melee Dmg
[3]+5% Reload on melee kill
[4]+10% Reload on melee kill
First of all, I think that the numbers in the brackets denote how many attachments need to be on said weapon for them to take effect([1] needing at least one attachment, [2] needing two, ect).
Now I was wondering if I'm at all right about this, or if I'm way off base. Also, say you have four mods with this same synergy. Do they stack? Will it double the boosts from on weapon synergies? On that same note, what if I were to put four Run n Gun mods on? Or two Outlaw and two Survivalist mods? Would I get all three synergy bonuses(Seeing as brutal goes up to [4] and the other two only go a as high as [2]).
I would really appreciate some help full input.
P.S. Sorry if the topic has already come up, but I didn;t have any luck finding the answers I'm looking for.

