I realize they are not loader rounds, but in heat treating WW bullets the hardness is only effected once the bullets have been immediately dropped in cold water, and even then if the bullets are sized after heat treating you will loose what you have gained, Heat treated bullets should be sized before the heat treatment, and then lubed only with a size larger sizing die than initially use. An example would be. If sized to say .310, before heat-treating they should be lubed with a .311 die.
So to get back to the beginning, even bullets cast from W/W will not harden from boiling them. Just me and in my younger days I did clean auto parts in Gasoline, But it just seems too many things can go wrong with all the Gas fumes.