Hi Duff Beer, I`ve been taking a close look at mine since your post.How to get 58 (barrel sleeve retainer) seperated from 48 (pump body) seems to be the real problem, and I have to say, much to my annoyance, that like you, I`m baffled at present,
Obviously stock screw 72 acts as lock between 48 & 58, but whether the i/d of 48 is threaded to take a male thread on the outside of 58 is unclear. I would think not because it would be difficult to grip the cone shape of 58 to tighten it on 48, and there are no signs of holes for, eg, a peg spanner on the back face of 58.On the other hand the assembly diagram could be interpreted as showing a thread
I did try gently tapping the back face of 58 with a copper drift (with 72 removed) but with no result.
Sorry to be unhelpful, I`m as puzzled as you!
Anyone else experienced this problem?