@Vverg
Well, he's got a pretty large variety of metals with different properties.
And he ought to be a gun otaku, meaning he knows a lot about guns.
And he's able to freely manipulate any metals as he wants.
Basically, he's got the Technology (knowledge) , Materials (Resources) and Production (metal manipulation) needed to do it.
Not saying it would succeed on the first try, but he can always just reuse the metal.