www.wheretoshoot.org is one option to try, haven't used the site in years, just google rifle ranges etc...you should come up with something, here in IL I find 100yd and 200yd even 200yd rangers are hard to comeby without being a member to some special range/club, so good luck!

It is a shame that more public rifle ranges to 300-500yds don't exist, at the very least 200yds needs to be the minimum.