Metro Exodus

There are two new weapons introduced in Sam's Story; the Sammy rifle and Stallion pistol. They each have their own upgrades to find. They will all be found in the Night Hunters' secret stashes, however you can find them in various other places too throughout the game and are likely to find them all before having found and entered all of the secret stashes if you're exploring. Just be sure whenever you see these two guns, to hold on it to take all of the available parts into your inventory. You acquire both guns at the start in the armoury you're required to enter and you should keep hold of both and use them since they're both very useful. Periodically go into workstations when you find them and equip/unequip every attachment so that everything you have found is sure to be counted.