Why would they do that? If you were selling something would you knock the price down without being asked? I sure don't.
Just ask. "Can you do a little better?" is a good one. "Got any wiggle room on the price?" That kind of thing. And be prepared if they say, "Nope, that's the best I can do." Then you either bite the bullet, or walk away, no hard feelings.
Factors to consider. How long has it been there? If it just hit the shelf today, you can't really expect them to drop the price. Again, why should they? The guy standing right beside you with his check-book in his hand might be looking for exactly what you're holding. The longer it's been there, the more likely you are to get a positive response to "Got any wiggle room?"
Another factor. What is it? That little 32 HE, is a pretty common gun, but it's not a high volume seller these days. It's taking up space in the case. They probably want to move it fast, they probably didn't pay much for it in the first place, so dropping the price might do it. Especially if the customer seems really interested in it, and the last person to look at it, was the guy who put it in the case. If it's a "Pre-27 with a 3 1/2" barrel...they might not be so quick to want to move it. The right buyer is out there. "If you don't want it, that guy behind you does." type thing. (I've actually had that happen to me. Hand the gun back, and the guy watching, says "I'll take it." And I've done it the other way too.
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It's all part of the game. Unfortunately I think, a lot of places are switching to the "no negotiation" policy. The price is on the tag, take it or leave it. I like a little dickering.
Edited to add: There is almost no wiggle room on new guns. I don't even ask. One reason I seldom buy a "new" gun. You'll find me on the "used" side most of the time.