I have a .223 Saiga already, a Romy G kit that I need to put together, a FAL, CETME and a Remington 700 in .308. I was considering doing this one as a pistol build so I wouldn't need to worry about 922r. I have limited tooling so that is why I was looking at those three particular rounds because I believe, and correct me if I am wrong, that they have a very similar base diameter to that of 7.62x39. I would have no problem with an 08 loading other than as of yet I do not have any reloading equipment, so using anything other than factory loads would be a no go and I do tend to like my face and hands as they are.
I'd like to note that I wasn't looking at the .30 RAR, I was looking at the 6.8 spc's parent round the actual .30 Remington. My thinking with that one is I would be able to deepen the chamber on an existing yugo barrel that I could get for cheap and have little other machining to do.
I'm really just looking to make a fun gun to build and shoot.