I believe only in California and another state out there may require a permit, but can otherwise be in your possession and purchased. For example, the company that makes the XM42 has been available on shelves in some major retail goods stores, and can be purchased over the counter easily.
Awesome Shotty by the way! If you are looking for some truly world class professionals in terms of getting you a blue job, I highly recommend Precision Bluing ( www.precisionbluing.com ) . They have a variety of finishes to choose from that will suite your taste. I believe they also deal with...