In McKinney there a couple other places as well:
Front Sight Firearms -- carries pistols and rifles (located off El Dorado next to Jack's Pub)
Tempesta Firearms -- has higher end classic firearms (the man cave is located in downtown square of McKinney)
Runner Runner Guns -- AR-15 parts, lowers, uppers, rifles only (across 75 from Cheaper than Dirt)
Runner Runner is so good that they are expanding into a much bigger store right now. I HIGHLY recommend these guys as I have been buying from them from the start. AR specialists and they have everything you could ever want for your AR plus they build them as well. The walls and cabinets are full of stuff you can touchy feely where most stores won't. Transfers are just $20 and I drive the extra miles just to keep going in.
Runner Runner is a MUST GO if you're into AR's.
http://www.runnerrunnerguns.com/
Runner Runner Guns
4.512 Google reviews
Gun Shop
Address: 2035 Central Cir Suite 108, McKinney, TX 75069
Phone214) 842-8163
Hours: Open today · 10:00 am – 6:00 pm