Not really information, just out of interest: several years ago I bought what was advertised as an Air Arms Chameleon at auction, very cheap, well not too dear. It was clearly based on an AA 100 action but covered in camo tape. On full inspection at home it was considerably ott so I proceeded to open it up. (remember that the SM100 etc came with a manual that told you how to adjust power level?). I found the rifle had been 'carbined' quite competently by lopping a couple of inches off the cylinder and welding the end back on i.e. there was no removable end plug although the filler valve unscrewed as normal. The main valve failed a short while later ... it had broken in the past and been fixed with araldite. I tried several times to make a new valve head but could not get it to hold air for more than a month despite new seals everywhere. I eventually sold it to an 'enthusiast' who wanted it despite the issues. I recall it had a competition trigger as well.
Ah, memories
Cheers, Phil