Zip Codes and Mailing addresses are weird things. I had an Aunt & Uncle that had a house over in Perl Mack (~72nd & Pecos), which was unincorporated Adams Co. Their mailing address was Denver. Later in the 70's they moved to around 74th & Sheridan, on the Westminster side of the Arvada/Westminster boundary. Their mailing address was Arvada.

That does suck W.R.T. the shipping of mags, guns etc.