Yup, there's not much volume needed to remove the sharp muzzle report on springers.
I made a small 5cm long single chamber moderator that works well...
The washer at the loading tap is a shim washer used to line up the tap with the barrel. Yours may have pinged off to oblivion or if you're very lucky...
Thanks again, I've been looking at things and I think I have found what keeps the loading mechanism in position. There are a couple of recessed areas...
You can buy a sheet of 1mm delrin 100mm x 100mm for £2.79 on the bay, cut the size you want with scissors/snips.
On a lathe the blade will waste 3mm...