I think the aluminum is popular based on 2 things. My nearby range, which allows steel but not aluminum, is now insisting on checking your ammo. That tells me many people are suddenly trying to come in with the Fed AL they got at WW. And the 9mm 100 pks, which were a hot item a while back, are sitting for days.
No Fed Al in any caliber on my last WW trip, but it was about as wiped out as I've ever seen it. Very little pistol ammo and no .22 as usual.