Si I have noticed that when screwing in the external velocity adjuster you can feel and hear the hammer spring binding. This is reduced by polishing the ends up, it is also improved by adding small mushrooms to each end. The spring needs shortening first, also played slightly with one at the back only.
I have managed 3ftp variation with weighed pellets after this.
I experienced low shots hitting the string level. This has since stopped since replacing the reg which I discovered was pushing out 120 bar.
Steyr LG110 FT, Sightron SIIISS 10-50x60 LRIRMH