I'm betting that unless your name is linked via business to a company that retails their products, you won't be able to walk in the door for a peek around any firearms factory in Europe as an individual. You might be able to do in in the USA, with the likes of Shiloh Arms or even Christian Sharps, but that's because they are semi-custom rifle builders. not commercially large ventures like those you have mentioned. Again, unless you are talking about bespoke companies, like Chapuis and their ilk, who have your deposit lodged firmly in their trading bank, you've probably had it.
Good luck, and let us know how it pans out for you.