They don't park the inside of any bbl I'm aware of. They park the outside.
RA uses chrome lining rather than nitriding. Supposedly, they tried nitriding and it caused overpressure issues or something; which to me sounds like whoever they had do it didn't do it correctly or the chamber wasn't reamed to the correct spec to begin with.
Pretty sure they are 4140 chromoly steel. Just normal bbls; I don't believe they are CHF.