Sorry about cluttering up the forum on this subject, but an important point just arose.
One of the trickiest (at least for me) points of assembling the QB comes when the Breech/receiver is mounted on the Main Tube. There are several bits that all have to "magically" come together simultaneously, and they don't always seem to want to cooperate. This makes for possible trouble for the HDD.
Specifically, there's the possibility for the hammer to slide backward to the end of the Pin Slot, carrying the Pin and HDD along for the ride. If this occurs, and if the HDD is allowed to ram into the end of the slot, the HDD "Wingtips" can get bent, disabling the HDD
If this does happen, and you notice it in time, the fix is easy. Just lift the Pin and HDD out of the Slot, bend the Wings back into position, and replace. The steel of the HDD is tough and ductile and nothing will be irreversibly damaged.
But it is aggravating and best avoided.
Thanks for your attention.