Ive also had great experiences with Engage Armament in Kensington, MD. Tom is very knowledgable and has great customer service. Will do business with him again.
Ive also heard great things about Gun Connection but have yet to go by there. I will one day soon.
So far, my votes go to:
The Cop Shop in Baltimore
Engage Armament in Kensington
There is also Atlantic Guns in both Silver Spring and Rockville. They have great selections, but their prices need a lot of work.
G34 OD, G21SF, G17, Advantage Arms LE 17-22 Kit
Sig P226 Elite, Sig P226 .22lr Conv. Kit, Sig 522 Classic
SilencerCo SS 22Sparrow & SilencerCo 9mm Osprey
Hornady LnL AP, 9mm & 45ACP