Replace main seals in Diana/Original Model 6G

These pages show the process of stripping an Original Model 6G (aka Diana) to replace the main compression seal.
This design is unique in having two identical opposed pistons which move in opposite directions, governed by a rack-and-pinion system to eliminate recoil. The dummy piston even has a piston seal washer but without any sealing lip.

The sequence of stripping (shown in following pages in pictures) is as follows:
1. Remove grip scales
2. Remove small pinion cover screws.
3. Remove pinion covers and pinions.
4. Remove lock screw from spring cap.
5. Remove grip frame.
6. Loosen spring cap 1 turn.
7. In jig, remove spring cap, springs and dummy piston.
8. Remove cocking lever pin.
9. Remove Trigger pin, and trigger and spring .
10.Remove cocking slide.
11.Remove main piston.

Remove the grip scales and the small locking screws holding the round covers of the pinions either side of the pistol body.


Unscrew the pinion covers, remembering which is Right and which is Left! The locking screw holes will not line up if they are reversed.


Remove the locking screw on the spring end cap.


Remove the 2 screws holding the grip frame to the pistol and remove the grip frame.


Put the pistol body in a metal smooth faced vice across the pinion holes and unscrew the spring end cap which may well be tight. Protect the end cap from the water-pump pliers with some scrap lead sheeting wrapped round it.

The spring cap has a shim and a plastic cushion under it to take some of the impact and to adjust the end gaps to be equal in the factory.