need help w this

[PF45]

hi guys; I scrach the throat on a mosin nagant trying to remove a stuck case.

How can I polish this, is just a small burr. When I chamber an empty case I can see the scrath on the case neck. Info apreciated in advance.

PF 45.

[Calamity Jake]

A little lapping compound or maybe JB bore paste on a tight fitting patch wrapped around an old bore brush then ran back and forth over the burr should remove it.
Lap a little then test.