Had the same problem with mine, power all over the shop over the chrono, bad grouping etc., gave the barrel a good clean and tried AA Express, they seem a lot better, doing around 800fps have also been told to clean the barrel regularly. The only reason I'm persevering with it is because I like the weight and it feels 'right', but if it ends up being too much hassle I'll get another TX for HFT, got one for FT and it is spot on and much more consistent/reliable than the Steyr.
Hope you get it sorted
TX200 - Big Nikko - FT
EV2 MKI - EB Sniper - HFT/FT
Steyr LG110 Hunter - SORTED! HURRAH
THANKS TO CHRIS C