hit and miss I'm afraid mate..... the one on my 100S is spot on, as is the custom one on my 100T, but there are one that are a bit out.
If you're interested A & M Custom Gunsmiths do a custom aluminium cylinder for the HW100, bigger, lighter, more shots per fill and an accurate gauge, Ask to speak to Adi, if you're interested tell him Darryl told you to call
Darryl