While we're talking about carbines and such, wouldn't it be a great time to look into an AR "pistol" with Sig's new "armbrace stock"? I have an M1A with standard 22" barrel, and I have thought more than once about how easy it would be to see me coming around a corner. If I was going to get an AR or urban/semi-urban scenarios, or just transition completely to an AR platform, I was thinking...why not go the AR pistol route with the above setup? That should reach 100-150 yards accurately with practice, I would think. Once SHTF, if it's REALLY bad, you can also always transfer over some regular AR furniture.
As a side note, is there an ATF regulation against putting suppressors on an AR "pistol?" If not, that plus the Sig brace would seem like an optimal combination.