HK416 Build – Required modifications

Use of the dual-sector gear requires trimming the height of the tappet plate such that it will return the nozzle for the 2nd half of each rotation. As it has been several years since my last DSG build, some other critical steps were forgotten and the results were…interesting.


Note that the unusual wear pattern on the tappet plate starts from the bottom, counter to the typical movement of the sector gear. This is caused by the backwind of the DSG against the tappet plate where the fin has sufficient space to allow the sector gear to wedge itself.  To prevent this from happening 2 small modifications were done:

  1. Shim the DSG slightly higher (0.2mm) so as to remove possibility of the sector cam being lodged again.
  2. Modify the anti-reversal latch to expose a 90-degree interface to the bevel gear. This ensures a solid lock-up against the bevel, preventing backwind. Although the current set of Siegetek instructions do not make mention of this, this was a modification that was required for previous generations of Siegeteks.


Mechbox will be re-assembled and tested again.

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