Using my own rig (both weapon and arm) for FPS character

Hey , is there any chance to use blend keys in 3dsmax to export my animations to ue4 for a fps character ?
and I want my own custom weapon rig to being used for animations ( cuz for animations I need to use a one mesh but ultra skinned for parts )

I tried to export my own rig to fps project but it separate’s the gun from the arm . I want to use my own rig with a biped arm skeleton to use my own animations in 3dsmax .
please stop advising me using the blender , I can not waist my time on that .
so ?
I’ve red this documents but it is nothing there to how to use our own rig and weapons .
see my reload animation in this picture :