TargetTalk

As you read on previous post, I bought a 4.5" bbl one for my wife. It seems its chamber is VERY tight - even more so than my 208s. CCI SVs have a hard time chambering, that is not unusual, but the SK Std + also has a hard time chambering 8-O What do I mean? I can not even push them in by hand. I use SKs in all kinds of match chamber 22 rifles, and have never had an issue.

I have cleaned its barrel and chamber every which way - except using a metal brush, nylon only. any ideas?

You could try a messing brush. Nylon doesnt do much.
You tried other ammo besides CCI and SK? RWS, Eley, etc?
If they're all tight, I'd say somethings wrong.
Otherwise, just change ammo.
Some guns just have issues with some ammo.
My Pardini SP had feeding issues with CCI

Use a 6mm bronze bore brush, it cannot hurt barrel steel.

If you have dry fired this gun with the chamber empty, you might have peened a dimple in the chamber. I did this on a High standard and had the same problems you describe. I fixed this with a slightly tapered punch. I was extremely careful not to expand the chamber or touch the rifling. Good luck
Chris