will you try to cast bullets out of the aluminum ?
No.
First reason: there are some rules regarding what bullets can be made out of, how thick their jackets are, what kind of core they might have etc. Basically, federal hand gun ammo rules have a list of things that are considered 'anti personnel' and therefore illegal. No titanium cores, jackets comprising more than 25% of the weight, etc etc etc. I don't recall if aluminum is in that list or not.... but I don't think it's worth the annoyance of looking it up again
.
Now, rifle rounds are fine, though.
The other reasons for it would be that aluminum might tear up your barrel, dunno about friction issues concerning stove piping and pressure spikes and such.
If I had a cheap p.o.s. rifle I didn't care about, maybe.
And lastly - you really wanna go from a heavy metal like lead to a super light metal like aluminum ? Just look at the differences between total copper bullets vs jacketed or cast lead. Or steel shot vs lead shot.
I suppose I could make a shotgun slug.