What I usually find works for both parties is to say to serious buyers is 'meet at XXX gun club and we'll shoot a round of skeet together and see how you get on with the gun'.You have to use judgement to see who is 'serious' and who just fancies lots of rounds of skeet with other peoples' best guns!
If you are in a big gun shop, they may be less inclined to do this with middle -price guns but if you are planning to spend big money, they really need to accommodate you.
I think it entirely reasonable for a seller not to allow an amateur to take away a gun worth thousands and try taking it to bits and to supervise any test firing of the gun before money has changed hands.
