Firearms and firearms laws question thread

It seems we have more and more people coming here asking general questions about firearms and firearms laws. It also seems we have a handful of people who have a pretty descent grasp of those issues, so I thought... let's bring the two together. If we're going to have an honest debate then we first need to answer people's questions who aren't as familiar with the issues as some of us are. This thread isn't about philosophical differences. We all approach the issue from different angles. This thread is about the weapons and the laws that surround them. So if you have a question about what's legal vs what isn't or about how certain types of weapons work... this is the place to ask and I'm sure many here will give you the best answer they can. I'll check back as often as I can to answer your questions.