I have walked up to the ticket counter several times and quietly announced that I needed to declare a firearm and people around me would back away. I have had female agents back up and look faint when I opened the gun case for them to inspect (with the gun clearly disassembled in pieces). They will sometimes attempt to attach the "declared unloaded firearm" tag to the outside of your bag. Wrong. Some agents have assumed that I was an LEO and handed me the wrong paperwork to fill out (which puts me in the position of impersonating a police officer). I kid you not. Know the rules. The TSA does not. Some of the agents don't either. Ask for a Supervisor if they don't know.
That's funny, actually. There were two counter agents, and the first one thought I was an air marshall. (Thanks for the compliment?) But the other one clearly knew what she was doing. Neither one was concerned or bothered. The first agent hadn't dealt with a declared firearm before, but the second was quite knowledgeable. The first agent initially thought the declared firearm tag went inside the locked gun case, but the other agent politely corrected her that it goes inside the luggage, but outside the locked firearm case.
Overall, just a better-than-expected experience.