Best source for this would the National Rifle Association. They keep these statistics to help with their legislative efforts. They do have a web site where you may find these figures on your own or you can write them with your question. They will be happy to help you.
depending on the rifle i would check ebay. or just google it.
Looking for a owners manual on a western field 22 rivle.
6
Try contacting the maker.
Very good
The National Rifle Association (NRA) represents the interests of gun owners and advocates for the protection of Second Amendment rights in the United States. It is one of the most influential gun rights organizations in the country and represents a wide range of firearm owners and enthusiasts.
Gun owners aren't "registered" like cars. One estimate is that there are @ 4 million or so gun owners.
See the link below for the Owners Manual for the Crosman 1077 air rifle
Impossible to answer. There is no registration of gun owners in the US, so no records for the information you ask for. Best estimate is several million.
No known web site.
what type of scope mounts do I need
See the link below for the Owners Manual.