Sniper Elite 3: Complete Weapons part location guide
Sniper Elite 3 has 15 Weapon Parts, if you manage to find all of them you will reach 100% game completion which will help you unlock "Dedicated soldier" trophy / achievement. The weapons are to be collected from only those precise enemies which have them. If you collect weapon parts you can customize the Sniper Rifle and upgrade the Binoculars. There are 2 weapon parts in each mission. The collection of weapons will be saved automatically even if you die in the game.
Here is the Sniper Elite 3 all Weapons part location guide