The left arm gun slots over the mini gun that comes with the figure, the right gun has a small peg that slots into a hole the battery cover slots into.
The gattling gun was is from the same line as above, I bought a extra shoulder mounted gun that came with the figure and you can use the screw that ataches it to articulated arm to screw the gattling gun in place.
Ps tried using magnets but didnt stick which makes me doubt the metal content of these die cast figures...