imported post
A shotgun with a 17" barrel is NOT a long gun under federal law. It is a Short Barrel Shotgun, and is an NFA-regulated item.
If you buy it ready-made with the short barrel and pistol grip from a registered manufacturer, there is a $5 transfer fee, but all NFA rules still apply (NFA background check, etc).
If you make it yourself by modifying a "regular" shotgun, there is a $200 "transfer fee" and you must possess the BATFE Tax Stamp and NFA paperwork to legally possess an SBS. And you'll need to start the process for the tax stamp BEFORE you modify the firearm, because you must have the stamp the instant you "take possession" of such an NFA-regulated item. And the minute you finish your modifications to a shotgun to make it an SBS, you have "taken possession" of it...
Good luck with that...
Carrying an NFA-regulated weapon on your person for personal defense is a risky game. If you should ever have to use it, or be stopped by an LEO and questioned about it, you'd better have a copy of the NFA paperwork and stamp in your wallet to prove it's legally possessed, or you're going to be looking at a VERY expensive and drawn-out encounter that will most likely involve handcuffs, the BATFE, possibly the FBI, and a LOT of lawyers.
And even if you are eventually cleared, you're going to have a heck of a time getting your SBS back, because most likely it's not going to be the local LEO's who end up with it, but rather the BATFE. And you're most likely going to have to sue them to get it back, because they are going to seize it under either the Federal Asset Forfeiture laws or the NFA laws which mean that you are guilty until proven innoscent. These types of sezures are often VERY troublesome, because they'll probably going to mark you in their database as being "ineligible" for owning NFA items, and the only way to get off that list--even if you are cleared by the courts, or your local LEA is to file a lawsuit against the feds. And believe me, they have a LOT more time, money, and lawyers than you do.
And of course, some states have laws restricting the carrying of concealed firearms above and beyond NFA rules. I can't speak to WA, but here in NC, the permit is entitled "Concealed Handgun Permit". And under our law (and federal law) an SBS is NOT a "handgun". So carrying an SBS concealed would not be legal in NC, or many other states with similar stipulations on their CC permits.
Of course, your laws bay be different out there, so do your research...