Rays hardware on singleton near downtown. They have a wide variety of used guns I recommend hitting them around Christmas because a lot of people sell off guns to buy gifts for their family.
+1 for porters army navy in Irving, I've known the porters my whole life great people. They have a great lay away program to as long as you keep in touch they will work with you.
If you're not opposed to trekking a bit further east, Ammo Depot in Caddo mills is about 40 mins east of downtown on I-30, and by far the best pricing around, they have some handguns there, but they are mostly geared for long rifles and militaria.
Further west of there in garland off of I-30 theres B&S Guns, I used to hate that place, but I guess over the last few years they've caught on, went in there a few months ago and their customer service improved 1000 fold. Prices on the other hand are a different story, decent prices on used guns and most of the new ones, but for a laugh, check out their prices on ammo! $60-something for a box of .45ACP hardballs, any brand...
S.A.W in the Mesquite/Sunnyvale area is a great shop specializing in your NFA needs, but par for the NFA course, fkin expensive!
Theres a new gun store at the intersection of I-30 and 635 in garland called Gun Zone, I still for the life of me cant figure out how in the hell to get there, can see it plain as day from the I-30 high five, it looks like its more on the westbound I-30 service road on the west side of 635, but I dont know how to navigate it, shares the building with some plumbing outfit called "Flow Plumbing". If any of you make it there before I do, please rate it!