I think the aforementioned Haenel 303 was part of the trade in which I acquired the Airsporter at Findlay this spring. I was ultimately able to get it apart, with the help of a 1/2" x 36" steel rod I got at Home Depot. A new piston head, oring, and buffer, and a Maccari .120 wire 32 coil spring, and all is well. I took the time to pre-set the spring to coil bind on a piece of all-thread, otherwise I never would have gotten it back together. A lot of work for 620 fps, but overall worth it. The Airsporter is a stunningly beautiful concealed underlever taploader. Certainly not user friendly as far as servicing, but a very unique rifle.
I did make sure to coat the threads of the end plug with anti-seize before reassembly, in case I ever have to go in again.
I think we're all Bozos on this bus.