[thegunsofNevada]

I dont know your skill level, but I would recomend aginst a shotgun. They can be very messy if you dont know what your doing, and having to put holes into something while not putting holes into everything isnt a shotguns job, unless your using slugs. That presents problems, too. Not to mention that shotguns are low capacity weapons...The most rounds ive ever seen is 16, and thats a stretch.

And, speaking in broad terms, shotguns are not effective at long to medium range.

My advice would be with something compact, semiauto, and with range and power. Something like a civvie version of a FN-FAL or HK G3A4K if your big, or perhaps a .223 if your not so big or compatent.