When buying the tax stamp, is it for the lower or the upper. If someone just wanted to buy an 8.5" barrel, do they need a tax stamp for it?
The registered part is the lower. You can buy short barrel uppers by themselves and use them on a pistol lower until your stamp comes back.
You can have any part be the ‘firearm’ component which is the basis of the SBR. For the same reasoning behind why the lower receiver is used for most serial number and markings, it’s best to do that on the lower as well.
Finally, Google is your friend. I wouldn’t be surprised if this is locked after my post, but this information is available. Not that it’s a huge inconvenience to answer it, but as you keep coming across questions it’s better to know how to use the resources already out there than be stuck waiting on forum replies. If you’re looking to do an SBR, there’s hundreds of questions you don’t even know you want to ask - so use tools like Google Site Search on here for best results with that.
I asked here because this seems like a great group of people and the internet is a dangerous place. People can post anything and i feel more comfortable directly asking people who have done sbr’s. How are Rainier barrels?