"frosted" ?
 

From time to time, I see references to a barrel:
Being "Frosted".

What does this mean?

Leaded?
Rusted?
Pitted?

Does it hurt accuracy?
It it a "safety" issue? (if it is shot)
Is it shootable?
Is it the same as "shot out"?

I have also seen references to a bore being "Dark"

What is THAT all about?

Initial corrosion in the bore (and often upon the exterior finish), will appear similar to frost on a windowpane. As it progresses, it will darken with oxidization turning it â??darkâ?� or rust color. Pitting generally follows.

Start with a mirror bright bore and a clean bullet, perfect lans and grooves, and as the wear progresses, as the corrosion progresses, the accuracy diminishes

Safety and shootability generally aren't issues on worn and corroded bores (other parts in the same condition ARE Questionable, however, especially Bolts, springs, chambers, firing pins and just about all internal small parts).

Extreme pinpoint accuracy may not be acheived, but I've got several old "plinkers" with rough bores that are great for killing tin cans.

Some of us who shoot 1,000 yards regularly go through all sorts of gyrations hoping for the perfect groups, including, but not limited to: Filing points on bullets to remove burrs, frequent and compulsive cleaning of the bore and chamber during shooting, lubrication of the bolt face, praying to the gods of gusts and breezes and miragesâ?¦