That is good to know Ed and Lakey, about how the rear sight should be.
I have put a plunger in mine, but between two springs with the right diameter (3.8 mm).
I didn't have one spring, but two small ones, if that makes sense.
I tried it with smaller diameter springs, but that didn't look/feel right.
The plunger comes from a red dot sight that I broke up to salvage any small parts: happy I did so.
The conclusion is that I must find a longer spring with 3.8 mm diameter.

Anyway.
Yesterday I spent about two happy hours shooting the Light Pattern.
It was windstill - perfect.
My maximum distance was 20 meters; I will do 10 and 20 meters again today, and then try 30.
Adjusting windage is a bit difficult; I leave the rear sight alone, but move the front sight with a punch and a hammer.
One knock at a time. If the pellet hits left, then the front sight must go right.

After some practice, I shot 4 out of 5 Nespresso cups at 20 meters.



I think I can conclude that this barrel is very good.