To answer the question you asked, yes it is poor etiquette. It would be about as poor form as asking a guy at a car show if you could drive his car or after complimenting him/her on his wife/husband and asking for a test drive.
Now that being said I have struck up conversations on the range out of pure curiosity on firearms that I am unfamiliar with or that have a place in my heart. The last most memorable one was a fella that had an African double rifle chambered in 50 OH MY GOD. I stood respectfully behind and to his right as he was doing his thing. When he finished and acknowledged me with a look, nod and grin I asked him “OK you are loading artillery shells in that. What is it?” He laughed and we had a great conversation about his rifle specifically and double rifles in general. I was completely uninformed as to how they “regulated” the barrels and learned a lot. The rifle was flat out STUNNING in fit, finish and craftsmanship and he handed it to me and pointed out several things that you would not notice looking at it. We probably talked for a half an hour.
Near the end he grins at me and says “Wana shoot it?” I declined initially telling him that it must cost $10 a round to load and I had already taken up too much of his range time. He laughed and handed me 2 of those monstrous rounds and said “Chicken?” Nope! I remembered what he said about the barrels being regulated and while the recoil was “stout” it was not unpleasant, the 2nd round followed the first and touched it. He looked at the target through his Swarovski spotting scope, shook his head and told me if I ever get to go hunting in Africa to call him and I can use the rifle. I still have his card.
Having a true curiosity will net you a good conversation and mebby a try. That is not poor etiquette.