Buy an airsoft gun. You can get a full metal gun (just like the real thing) for $400 that shoots plastic bb's accurately out to about 50 ft. in semi,burst-or full auto
www.classicarmy.com
or
www.patriotairsoft.com if you want plastic guns that cost less and still really fun to play with. $10-50 range. The owner is a friend of mine and is really good to his customers.
Chase