Hi, I’m still stuck trying to figure this out.
What would you do If you want to use IK to keep left hand of your character on the rifle he’s holding?
I did this and works well when I’m idle but when I start moving my FABRIK becomes useless.
Here you can see a video:
Notice how when I start to move my left hand goes out of place with fingers clipping with the rifle D: . I simply placed a fabrik node in my custom state in default state machine where I only have rifle blendspace and fabrik ( I manually placed left hand on my rifle where I wanted it to be)
These are my settings:
And this is what I have in my state:
I didn’t find any video or tutorial explaining this, the only tutorials about this show how to keeps left hand on rifle with character idle animation but without explaining how to keeps left hand on wep while walking or running.
I hope that here somebody can advice me what to do 
P.S:I’m using infiltrator model by Epic Games and animations from Free Animation Pack on UE4 MarketPlace.