Well, it’s my understanding that there have been 3 BCG’s for the KS-47. The first gen were pretty much just standard AR BCG’s with 7.62x39 bolts. The second gen were labeled Hybrid and basically have some machine work to the underside to remove material to allow the BCG to clear the AK mag feed limps and they chamfered two of the bolt lugs for the same reason. The newest BCGs they are using are just second gen BCGs with Tool Craft enhanced extractors.
There are some pics in this thread. Hope this helps
Why the KS-47 BCG is different - PSA Products / KS-47 - Palmetto State Armory | Forum