The most important use is verifying how well the barrel bore has been cleaned. When shooting ammunition, carbon will build up inside and start to degrade accuracy. The Teslong sees carbon deposits in all places inside the lands and grooves of the rifling. Brushing out carbon with solvents and bronze brushes removes most of this deposit and restores top accuracy. The bore scope verifies if more cleaning is needed.
The second major use is to see copper metal build up inside the bore. Bullets shed copper molecules when fired from heat and friction. It will build up on the steel bore over many shots. Too much copper will give poor accuracy when shooting. The Teslong can verify how well copper is removed. Many new shooters are discovering they are not cleaning their guns properly.
The third important thing is seeing how much erosion is developing with continued firing of ammunition. Very high flame temperatures, above the melting point of barrel steel, will in milliseconds at a shot burn away steel metal. Over many shots too much metal burned away will produce poor rifle accuracy. The Teslong can tell an experienced shooter how much life might be left in a barrel. When buying a used rifle, a proper selling price can be established based on how much erosion can be seen.
The bore scope can see any manufacturing flaws in a new unfired gun barrel, and to help determine why a new rifle may shoot with poor accuracy.