I don't have the patience, but my brother had a single shot bolt action 50 BMG. Very accurate and would go a long way.
Holy shit! BANG! I freakin loved pulling the trigger on that rifle! We still have a chunk of 1.25" structural steel with many holes clean through.
It had a Walther barrel and the rest was custom made. With the muzzle brake, it was a sweetheart to shoot. Less kick than a 12ga.