I tuned a HW30s .177 with some shortened parts of a partly used 25mm HW50 Vortek-kit. Spring, parts of rear guide, top hat and Vortek piston seal. Clean, debur, polish and MoS2-regrease as always plus some barrel bore polish awa trigger tune. Resulting in 8+fpe with any tested pellet (836! measured shots with 29 different pellet types and/or sizes) and a very nice shooting manner. Best pellet was JSB Exact Express 4,52 / 7,9 gr (381 measured shots) producing 8,5 fpe / 697,6 fps / max dev 2,8% / std dev 3,8 fps Scoped I could easily hold 20mm groups at 30 m shooting seated with foreshaft on stockhand on Caldwell but maybe the small gun was little bit over powered. Main problem for accuracy at this airgun was the ball barrel lock. Initially it wasn't closing repeatingly properly - as I had to find out due to improper fitting of cocking rod thus resulting in galling at the underside of the sys-tube and early stopping of barrel locking process. Quite some grinding off the uper sides of the cocking links solved the problem. Still think that this gun was quite a lemon but after a lot of work and pellet testing it shot quite decently. Anyway - no intention to touch one of those anymore.