My new HW99S (.177) was underpowered from the start so I polished and re-lubed the internals, still only getting about 9ftlbs. I ordered a Titan #1 spring (their recommendation for the 99) but it was too wide to fit in the piston with a sleeve in place. Original spring 20mm O/D, Titan #1 21mm O/D. I did try thinning the Titan down a bit but it wasn’t successful.
So I looked through Titan’s list and ordered a #7 , 19.5mm O/D with wire 0.05 thicker than the #1, slightly less I/D. Fitted it today (without any cutting). It took a fair bit of effort to cock and fired with a bit of a jump – however it only produced 8.8ftlbs!
I’m stumped. Where do I go from here? I’d much rather fix it myself than send it off.