Check out www.rmgo.org

There is a capacity ban on magazines of 21 rounds or more. Even ifyour passing through Denver, and have a 30 round mag, you get pulled over, problems can arise. Just get the 20 round pmags for your AR and you will be fine. DO not chamber a round and then add that 21st round or it can be a hassle for you.

Id move out of the C&C of Denver if i were you. YMMV