Help with Martini Henry Barrel

[Vossie]

I have managed to get an internal look at the barrel, a bore light looked great but a camera showed a different story. The barrel has been cleaned but this remained.
Any ideas of what this is and how to remove it.

[ukrifleman]

I would suggest that a bore camera will inevitably show things you don't want to see!
Even a `mint` bore will show blemishes when viewed up close and personal with a bore camera.
When you are satisfied that the bore is clean, slug it to get a true picture of its condition and dimensions.

ukrifleman

[Vossie]

Cheers, I have cleaned this bore to within an inch of it's life.
So I was stumped as to what this could be.
I certainly will slug it now.