While I've not messed with aluminum framed guns, anytime I have an aluminum part on a car (intake manifolds, heads, etc. I always use something like form a gasket on the threads to keep the steel bolts/screws from corroding/galvanizing the aluminum threads.
While not really possible here, in a car I use studs when ever possible (so I don't have to run the steel bolts in/out of the aluminum threads, but sometimes you can't use a stud and you have to use a bolt/screw. Even then the insulation, provided by the blue form a gasket, seems to keep the steel from screwing up the aluminum threads.
If I had an aluminum framed gun, I'd try the form a gasket on the threads of the bolt just for insurance.