Bullet Case

{x}{t}, for every mana tapped summon one bullet token
{t}, add one mana of any color to your mana pool
{x}{t}, choose target artifact. That artifact becomes an artifact creature, it gains +x/+x. X=mana spent.
{w}{w}{u}{u}{r}{r}{5}{t}: destroy 1d6 creatures, add the power and toughness of those creatures together, you gain that many bullet tokens