I ordered a complete bolt assembly within 24 hours of their offering the bolts on their website. I still have not received the bolt, but all the guts came within a few days.
Last week I did a USGI bolt to Polytech receiver conversion and when I was finishing assembly I used the 762MM Firearms firing pin, extractor, extractor spring & detent, ejector spring and ejector.
The Winchester bolt that I had so carefully fit and lapped to the Polytech receiver would not close with the 762MM Firearms extractor in it. This is on the indexed Chinese barrel.
Looking at the extractor you can see some subtle differences. The extractor on the left is the 762MM Firearms. The extractor on the right came from my CMP TRW parts kit, and looks the same as the extractors I bought years ago from Numrich, one of which I used to fix the issue in the Poly. The bolt does close with that Numrich extractor.
Here's the two extractors in an unused TRW bolt. First the (probable) USGI type that worked in my Poly/Win.
Here's the 762MM Firearms extractor that was hitting my barrel face and keeping the bolt from closing.
Again, I have not tried the extractor in any other rifle. I have not yet contacted 762MM about it, and do not know if this would be a rare issue caused by the Poly barrel or what. I just noticed the thread and figure I'd share my limited experiences.
This weekend I should have the opportunity to pull out some other rifles and try the 762MM extractor in those which do not have Chinese barrels in them and see if the problem exists there.
SS