I've never had this particular issue. Problem is you have no idea if a custom tight reamer was used ect. In you pictures and from your description it seems the problem is the throat/freebore. I see no marks from the lands & no marks on the shoulder datum of the case.
I'd still pick up a go gauge & check but that doesn't look like the problem.
I have had a short reamed 6.5C that wouldn't close on go gauge. It was short enough that factory 130 prime ammo wouldn't close (AR barrel was Larue). My solution for that is the same I'd due in your shoes.
Clymer finish reamer off the shelf at Brownells with a few bushings cost about $200. I just turned by hand with a tap wrench & some tap magic cutting oil. Worked like a champ, gun hammers.
Just stop when you hit the shoulder and should be good to go.
If you don't have a barrel vise then pick up one of the PTG extensions from Midway & you wouldn't even need to remove the barrel.
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