Winchester 1917 way off

[Bruce_in_Oz]

Mil-spec barrel evaluation usually involved a "target" consisting of a white background with a vertical black bar on it

A straight barrel will show even sized and shaped reflections of the black line on the lands,

Bent and / or worn barrels reflect distorted versions of the black line.

EMEI / EMER etc. paperwork for general small arms maintenance techniques should provide details.

A different method: