I have been looking at the Rock River AR 15 pistols, and some of the other brands. I see that some put a foam padding on the buffer tube. I was wondering if anyone has heard if the ATF puts any limit on what you do with the tube. I know if it has a "stock" the pistol becomes a SBR, but at what point does added on padding become a stock? I see that a tube on an AR is not a stock, but if you look at a Rossi Ranch Hand you will see that "pistol" clearly has a whole lot more material (stock?) at the rear than is mechanically required by the action. The Ranch Hand looks to me like it could be fired from the shoulder. In fact, to me the Ranch Hand looks like a SBR with a short stock. http://www.rossiusa.com/product-list.cfm?category=17 So, has anybody heard anything about adding additional padding to the buffer tube of an AR pistol?