Schematic for the HW45 on Chambers site - https://www.gunspares.co.uk/showcatimage.asp?id=24564
haven't owned a HW45 for 15 years or more...only other thing I can think of without going inside is to check your trigger pull weight and adjust if necessary...
Edit: ...and yep, that sounds like the screw that I meant - C1077, cylinder lockscrew