I am having the same problem with my early mk2 after fitting the Vortek breech seal. Underlever much harder to close and bends the barrel downward resulting with POI drop ~60mm at 16m.
Wondering about seal thickness as I measured HW (old, may be original): 4.1mm and Vortek 4.6 with a much harder compound.

Quote Originally Posted by AC all day View Post
... The lip on the compression chamber is 2/10ths of a mm...
Could someone explain what/where this lip is please .