Just wanted to say this thread has saved my sanity. Stripper down my 2250 last weekend re-crowned barrel and cleaned out bore. Expected to get really good groups when firing again only to find my first 40 or so shots were all over. I was thinking I must have bu**erd up the crown. Read this article. Shot another 30 or so pellets and the grouping has now come back. Although I have swapped from Crosman Premier to RWS superdome.
I don’t know if anyone else has noticed that every so often the Premier seem to just have one shot that goes off, or is it just me.