Shooting technical advice
Striking off is the final stage of shotgun barrel finishing, in which they are brought to an elegant taper and smoothed.
This final smoothing and polishing process is important, in that if it is not done properly file marks and roughness will show through the blacking or blueing.
So yes, it is easy for anyone to see.
Well struck-off barrels have a totally smooth and even finish, while if the work has been done less well, any marks not eradicated will show through the blacking.
Another sign that the tubes have been properly struck off is the regularity of the wall thickness at the muzzles – any heavy handedness will show up via one side being thinner than the other.