Reply To: found an air rifle under my shed. ..
Be aware any volatile oil in the compression chamber, or barrel, will ignite under pressure, as when the gun is fired and the spring forces the piston forward.
There are several non-dieseling lubes/greases available for spring compressed air guns.
Your biggest rebuild challenge will be compressing the spring after you have everything taken apart and cleaned up. It takes a special tool to do this. Ask around the forum, as it is likely someone can help you out with that.
That’s a classic high quality air gun…worth the time and effort to restore it.