Crosman had made over 100 different models. It would help if you stated the model you want to reassemble.
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.
Crosman does. see the link below for the parts list and how to contact Crosman.
See the Crosman link below.
Crosman still has parts for this rifle. contact Crosman at the link below (Customer service) and order the parts you need.
In 1977 The Benjamin Rifle company purchased Sheridan air gun company. In 1992 Crosman purchased Benjamin. So now Crosman owns both Benjamin and Sheridan.
Crosman started making the Raven's in 2008.
It all depends on what is wrong with it.
CROSMAN 2100 You can find CROSMAN Parts and manuals at ( see the link below) This should give you a diagram on how to dissamble a crosman 2100.
You can still order 1077 parts from Crosman in New York. See the parts and owners manuals link below. Then contact Crosman Customer service and order your parts.
The Crosman 140 Air Rifle was made from 1954 to 1968 in four different variations. Crosman no longer makes parts for the rifle but you can still get it repaired. The Crosman home page offers a "Find a repair center" button on their first page. From there you can locate a center that has parts for your rifle. See the related link.