50BMG? Get Ed Hubel's 12 gauge from hell. Want near-NE performance at slightly more than. 577 Tyrannosaur is probably the cheapest of the bunch at a couple thousand for the rifle and about $35 per round.700 is most expensive at $80-$100 per round and forget about rifle cost. How much are you willing to spend, and what do you mean by 'more power'? If you want short range(100 yards or less) and money is no object there's a lot to be said for the big Nitro Express rounds(.577.