The infantry school in Gagetown has both the C7A2 and the C9A2, I have used both of them. The C9, major change is the barrell is drastically shorter, some people say its the ‘jump‘ version, we were told it is for FIBUA, shorter barrel, easier around corners and what not. The presser switch is for the PAX 4 sighting system, did the trial on them a couple of months ago. It‘s an IR sighting system, used in conjuction with a helmet mounted monocular.