Necro posting...
I started researching this to try and determine if the relatively few OOB detonations resulting destroyed receivers were related to the batch of bad Firing Pin Blocks (see
here and
here) or perhaps some fundamental flaw in the effort to make the S1 difficult/impossible to convert to an A1.
Based on what I've seen here and in other forums, the key differences between the A1 and the S1 are almost exclusively in the fire controls contained in the Trigger Unit Casing, however in see these two images of the bolt, even without getting a micrometer and measuring everything, the bolt is different as well:
While I am still very much inclined to believe that the issue was the defective FPBs, it is still worth noting that the differences are not exclusive to the Trigger Unit Casing.
