With a domain like gunexport.com it would always be best to approach companies already in the field as its specific to their business. If they decline, they may know someone else that would have an interest.
You could always send emails to more than one company. There may be a gun export company wanting the right name as export.com is already taken, established and recognisable.
Supposing they have trademark on the name; what happens? Have you checked for the trade mark right? If you haven't, please do, before writing them on their trademark right, so that you don't infringe . Or what are people thinking of my submission.
If there is no trademark infringement for the the keyword; you have a premium domain that is even better than their gun-export.com.
I wish you good luck.