Part 10 and 11 are the nozzle return spring and stopper. They pull back the nozzle during recoil.
With the block and nozzle out, put nozzle into block first. You will see on the left a channel where Part 10 and 11 is supposed to go (if looking down the nozzle hole), slide spring into channel and place stopper into spring making sure thin half of stopper goes into the nozzel return spring.
Wiggle block assembly into slide.
Use a small allen key to hold stopper in while you wiggle the block down into place. Once flush you should not see any of Part 10 or 11.
That's it, push nozzle forward and it should spring back on it's own.