SS192 is not an AP round and its sales have never been restricted to civilians. It is the predeccesor to SS195, the sporting round, and differs only in the type of primer used.It is no longer manufactured.
SS190 is the AP round and the BATF doesn't allow civilian ownership of it.
SS191 is the training round for SS190 and is regulated, I believe by FN against civilian ownership.
There's a couple other rounds, some restricted and some discontinued.
Also the bullets don't tumble. There's a lot of misinformation about the 5.7 round out there anyone interested in learning more about it should check out
www.fivesevenforums.comThe stopping power thing can be argued all day. I don't really know the answer. Though I will say having 50 rounds of ammo in a very compact carbine has got to be usefull.