It's it's own system, based off of Bolt Action Version 1. It's kind of like Bolt action 1.5. For some asinine reason nobody at Warlord told the K47 team about
BA 2.0 so they ended up releasing K47 a month before 2.0 dropped, which really hurt initial interest in some areas. Theyre working on updating it to 2.0 though, and honestly after skimming through both books it wouldnt be too hard to house rule the changes in. It's just annoying that you have to in the first place

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All you would need is the k47 book, it has everything, much like the normal Bolt action book.
No idea on player support though. I've not found a big group for historicals in my area yet so I have no idea if it's taken off elsewhere. People love the models but I've seen very little gameplay discussion. On the bright side, most of your army will be bog standard WWII units, so you'd be able to play regular bolt action fairly easily