I've a couple of Magnums, A mk1 and a mk2, Have to say, The breech seal being held in place in the mk2 is a huge improvement as I was shooting my mk1...
It was quite a complicated situation at the time because Milbro were still selling UK made Dianas (Mod 79 and 80 break barrels). M&G were selling air...
Thanks for posting that article. Interesting about the position of the transfer port. I'm not sure if mine is clipping pellets. Just need to do a bit...