Personally that looks like a typical Funnel type lead that was common back then. I don't think I would do a thing with it till you shoot it using proper bullets in it. Every BPCR rifle I have has that type of throat except one and they shoot quite well.
The photo below has a throat similar except it's not a bottle necked case but the lead is close and it will hold it's own for accuracy.

[Linked Image]

Last edited by Kurt71; 12/26/14.