The rib extension of my very well used but still tight and on-face 1906 No. 00.



The entire extension fits into the slot in the breech (Wedge #1). The "Double Cross-locking Rotary Bolt" rotates into the mortise (Wedge #2) and over the flange at the end of the extension (Wedge #3). #2 and #3 surfaces are both beveled and may be built up by welding, then filed to tighten the lock-up.

Occasionally the locking bolt is too worn and must be replaced.