It would appear your barrels have been bearing surface re-sleeved , mine has the short bearing surface like one you show but No counter bore to front barrel

on my unmolested barrel the front of the bearing is the front of the barrel with a 60* countersink to rifling in the barrel .


No sleeve !
Yours appear to be counter bore re crowned barrels .
I suggest you get some Evapo-Rust (TM) and and submerge the corroded one only to the rust line and let sit for 24-48 hr once rinsed you will have white metal , oil and shoot .
Evapo-Rust (TM) will remove any iron oxide this includes park and bluing !! But will touch no other metal type or eat into unoxidized steel at all .
https://www.evaporust.com/?gclid=CIelkZzFocgCFQyPHwodlcYEpA