Maybe just inside the chamber mouth? Would need to measure the diameter of the rim-recess to see if it matches the diameter of the ring visible at the muzzle.
And don't be shy about filing off that burr on the extractor-plate, and check that the firing-pin retracts easily to avoid any damage to its tip.
Fun times ahead!
-------------------- Marrakai
When the bull drops, the bullshit stops!
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www.marrakai-adventure.com.au