You can't it's not designed to be a repeater.
The Crosman 760 doesn't shoot Bullets it shoots BB's or .177 caliber Pellets.
Crosman has some parts available online. See the link below for all the Crosman rifle parts manuals and owners manuals. You can order parts from Crosman.
There are several versions of the 760. See the link below for all of the crosman models with dates and manuals.
Crosman has made 5 or 6 versions of the 760 and has parts available (See the link below for the older 760 parts list. ) I would contact Crosman Customer service to order the parts (see the Link below)
The CROSMAN 760 Powermaster started production in 1966 then went through 8 different changes and ended in 1991
See the link below.
Crosman has both the owners manual and parts manual online. See the link below and download your 760 parts manual. Then contact Crosman customer service and order the parts. Everything is on the opening home page for Crosman at the bottom of the page.
See the Crosman link below for the diagram.
There are several variations of this rifle model 760. I suggest you contact Crosman corp. They still have some parts available Go to www.crosman.com and contact "customer service."
There are 12 versions of the Crosman 760. Which one do you want.... See the link below
See the link below for the owners manual.
Both Daisy and Crosman made air guns/BB for Sears. I believe you are asking about the Crosman model 760 pump repeater Rifle. there are several variation's of the 760 starting in 1966 all the way to today. However Sears stopped selling gun in 1980 so yours is before 1980. I would think yours would be closer to the 1960 date because the later sears model 760 carried a model number of 126.19331.go to http://www.pyramydair.com/ and do a search for 760 to see if this rifle looks similar to your rifle.