My guess would be someone did not use the torque plates on the barrels when sizing/honing them. The torque plates cause the barrels to act like they are under assembled stress condition so, are a necessity to keep distortion @ a minimum
HEATWhat would cause this rusty looking spot on cylinders? Motor is 120r with 4.125" cylinders View attachment 275241 View attachment 275242
Yes they were brand new and perfect.Did you see the cylinders before they were installed?