Thanks for the replies. I can confirm they (not bufferless) do fit, since I just got one 😉
If anyone is interested, it came with a buffer which weighs 5.64 oz. The BCG weighs 15.16 oz. At 21 oz combined, it's a little underweight but I haven't shot it yet. I also have a 11oz KAK buffer to try.
The BCA buffer feels like a solid chunk of steel with no sliding weights inside (I'll probably take it apart to double check) while the KAK buffer looks and feels nice with sliding weights. The KAK is also slightly longer, 101.5mm vs 100mm.