Both the close combat arm and multi melta arm are magnetized, but they are oriented in such a way that the pieces aren't interchangeable. The solution? More magnets and some pins to boot.
With a little force the multi melta was slipped from it's elbow joint. The tab which slots into the elbow joint will be used as the attach point. The one from the multi melta will serve well for the right arm. A second elbow tab was prepared with magnets for the left arm.
I look forward in testing some of the new arsenal on the table sometime soon.