SBR, SBS, AOW, barrel length ?????

Ok, if you have an AK pistol (such as a Draco) with a barrel less then 16" you can always go shorter on the barrel. The Draco has an 11" barrel and if a person wanted to put an 8" barrel on it it wouldnt be a problem because the gun started life as a pistol. Same thing with an AR, if you had a 10" AR pistol, that was made as a pistol, you could swap out for a 7.5" barrel with no problem as long as it was never converted from a pistol to a rifle. I see guys over at the AK Files all the time that build their parts kits into pistols.

So basically, if a rifle platform gun started life as a pistol (AK/AR pistol) you are free to change barrel length with no regards.

So........

How come you can't take a shotgun that was born as a pistol (Mossberg Rollong Thunder, Tactical Cruiser) and install a shorter barrel on it, of couse keeping it in PGO furniture?

Why are shotgun pistols regulated by ATF as AOW and centerfire pistols aren't. You can put any length barrel you want on an AR15 Pistol lower. But not any length shotgun barrel on a 12ga pistol.

Wow, that makes no sense to me at all.

I recently finished an AK pistol build out of a Draco pistol. I shortened the barrel and gas system 4 inches. Thats perfectly legal because the gun was manufactured as a pistol.

I was explaining my build with the guy (fairly respected) that works at my local gun shop.
He says "Dont get caught with that thing". I told him it was perfectly legal to shorten the barrel of a pistol. He asked "Would you show that thing to an ATF agent?" I said "YUP". I tried to explain to him about how and why it was not an illegal firearm. Thats when he stumped me with the shotgun barrel length question.

I knew that PGO shotguns from the factory still had to maintain an 18" bbl. Just didnt know why.