Planning on Godzilla attacking in the near future or something? Maybe you want to set off some avalanches or something, its about the only practical use for it.
You should check out Hubel458's 12 GA rifle from hell. It uses a .50 BMG brass necked up to a straight walled cartridge and loaded with a 12 GA slug.
http://thefiringline.com/forums/show...ifle+from+hell