I will mention that when I bought my Weihrauch the barrel and chamber were filthy, covered in any-rust, and I had to give the bugger a right old clean before I used it. I mean I seriously had to spend a long time cleaning it before it came up spotless.
Once cleaned, it shot like a house on fire.
I had trouble with one of my old CZ rimfires failing to extract thick-rim (Federal) ammo (have you measured the rims of the different types of ammo?) and the issue was the extractor.