Pump Action Repeater Plans, 1950s

Here's a set of plans from a 1950s issue of Popular Mechanics, if memory serves. You'll have to modify the stock design a bit to turn the shoulder stock into a pistol grip, but otherwise it's pretty straight forward woodworking. This design could easily be modified to use with one of those 50# or 80# replacement prods that you can easily find on Ebay.

This one's a lot classier than the Chinese Repeater, IMHO.

http://www.makecrossbows.com/crossbow-building-plans/