In modern gun literature somehow was accepted the designation as the Mosin rifle as "Mosin-Nagant". And this is wrong, these are two different rifles: They took part in the competition for the Russian Imperial army, and both were accepted by the Commission, but only the Mosin rifle went into production. If we talk about the similarity of designs, the Mosin rifle has some similarities with the rifle Berdan-2, which 20 years was in service with the Russian army. Here's an article about Mosin and Nagant rifles written by a good friend of mine. It is in Russian, but you can see the pictures https://litresp.ru/chitat/ru/Ч/chelnokov-sergej/mosin-vs-nagant The reason for the loss of Nagant were two small screws. The military leadership considered that it was unacceptable for a military rifle. In the bolt Mosin no screws . In Russian it sounds especially strange, because "Nagant" is in common parlance the name of not only revolvers, but also any short-barreled weapon, so revolver Nagan was widespread and popular.