In my opinion, the carded black rust on the outside and uncarded black rust on the inside are the same thing. The key is proper rinsing and/or neutralization, then drying, of the inner void.

Shooting oil in there might not hurt either. Sure, it causes problems in a rust blue, but leave that for the next bozo to worry about in 50 years.

And, as Mark has pointed out, the inside should have an added tin coating and rosin residue to help fight corrosion.