Given that 7 RUM brass is $2 to $3 per stick, IF available. And given that it is the same case length as 7 STW and 300H&H brass. Any reason that 7 RUM brass could not be fire formed from 7 STW, or, necked down 300H&H brass ?

Have a quantity of both of the latter on hand. And disinclined to spend $2+ per stick for the former... Do-able? Caveats?