Crosman has the parts diagram online. There were 3 different versions. See the link below for the first version. http://www.crosman.com/pdf/manuals/crosman/766/C766-EVP1.pdf
See the attacked link from Crosman for the parts diagram. See the Link Below.
Crosman had made over 100 different models. It would help if you stated the model you want to reassemble.
Crosman offers a service to locate repair shops that repair older Crosman air rifles. See the link below
Crosman offers a service to locate shops that repair air guns that are out of warranty. This service is free. See the link below. http://www.crosman.com/cs/service-center
You have blown seals or O-Rings. The rifle was made from 1975 to 1982. Crosman no longer makes parts for this airgun. BUT they offer a service to locate repair shops that repair the rifle. See the link Below. But first consider this. IF the rifle was in working order AND it was in perfect shape it would be worth around $50 to $60. Is it worth repairing? It would cost you almost that much to have it repaired. Today you can purchase a brand new Crosman 2100 ( almost Identical to your old 766 ) for $60 through "Pyramyd air" See the link below. It's up to you.
See the CROSMAN Link below.
See the link below for the Owners Manual for the Crosman 1077 air rifle
Crosman no longer has parts for this rifle. However there are independent shops that repair older Crosman air guns. Crosman offers a free service to locate these shops. see the link below.
You need to state the model number. If you want to take the time go to the Crosman link below and locate your model it will most likely have a parts diagram to identify parts and their location in the pistol. Click on "download a manual" at the bottom of the linked page.
Crosman does. see the link below for the parts list and how to contact Crosman.
See the Crosman link below.