Parts now fitted to my 250.
The buffer washer at the rear seems to be unobtainable so I made one out of a nylon plumbing washer.
A little bit fiddly to reassemble, the parts kept jamming as I slid the assembly together. Must have been me doing something wrong.
I just kept repeating the process until it suddenly went in smoothly.
There is almost no spring compression effort to put this back.
Held it in with one hand while I pushed the rear locking pin in with the other.

I did a few test shots to check all was ok.
This rifle is a low powered target rifle, as I remember the pellets would flatten on a steel back stop.
Now after using modern lubricants the pellets are disentegrating against the back stop.

When I get to a range I will do some accuracy tests to see if it is still as good as it used to be.

It used to put ten pellets through one very small hole at ten yards
(no metric here).

As I am a bit weaker with age, and the gun weighs about 12 pounds, I will use a rest to check this.