hi heds
i started with a hatsan mod60s and i had no problem fitting a silencer to it, all i did was to twist off the fore sight with mole grips, cut off the reduced tip of barrel then filled flat, re-crowned the barrel.
then it was just a case of getting a silencer adapter and fitting it, as the adapter is secured via a grub scew i also used epoxy resin to fix into place then fit silencer of choice real easy to do and well worth it too people tend to slag this rifle off but for the money it is a cracke,r i also got a tuning kit from this fella http://www.woodfield-gcp.co.uk/springtuning.htm