Ok, I have returned not one, but two guns to a shop before. Of course, they were both defective pieces of crapola... Rossi 971 revolvers, and both of them started jamming (yes, a revolver JAMMING!!!) after you got it a little dirty (100 rounds or so). But if you want to return guns you are bored with, or something like that, I'd talk it over, but don't plan to get far.
The problem with this industry is that we don't have gun shops that believe that the customer is most important thing. I've heard of people being thrown out of shops for asking simple questions before they buy their first gun, and other similar stories. Hope that you get the manager or owner in a good mood, and just ask. You can't say as though you didn't try. Be very polite, apologetic, and offer to spend the money right there on something else. If the gun is unfired, or still with the dealer (for waiting period, etc), you may have a chance. Good luck!!!