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I decided to get one of these to see what’s going on inside the barrels. What surprised me was all the scratches on the lands of my cz 457 barrels. These look to be from the factory because they are perpendicular to the rifling. I use a Bore tech bore guide and .20 Bore tech rod.
I also have a Lilja custom barrel and that barrel is perfect except for the carbon ring in the chamber. I got that all cleaned up so I guess the scope is a useful tool.
Carbon ring on the Lilja barrel.
All cleaned now.
Lilja barrel,