It's been awhile since I was on the KTOG SU-16 forum. I had the impression from your statement that my -16 could be converted to take the 300 BLK. Seems the factory is using the basic frame and putting a 300 BLK barrel in it, along with a compact forend, to make the SU-300BLK. Still won't be able to swap out barrels/forends like the AR.

There is a lot of interest in this conversion. Will be interesting to follow it's progress.