I have a question about one of my AKs that I'm going to bring back to island with me next month.  It's a Zastava M85 Underfolding Rifle with faux barrel extension.

The measurement that HPD will do is my question. 

When HPD measures the barrel length, would they start at the receiver or measure where the barrel begins "at the bolt face with the bolt closed" inside the rifle receiver?

If they measure from the bolt face with the bolt closed then I have a 16 /2 " barrel.  I have a 16 1/2" wood dowel in it and it sits flush with the bolt face with the bolt closed.

If they measure from the beginning of the receiver then I have a 15" barrel.

Any assistance would be appreciated.

Found the answer, it's a 16 1/2" barrel

https://www.atf.gov/file/58196/download

They'll measure from the "rear most part of the barrel.
Almost all AK's have barrels pressed into a trunnion, making them "shorter" than 16" if measured from the rear of the receiver.

If I remember correctly, the ATF method is a dowel placed in the barrel till it contacts the closed bolt of the rifle.  The measurement from there to the end of the permanently attached muzzle device is the length of the barrel.

If I remember correctly, the ATF method is a dowel placed in the barrel till it contacts the closed bolt of the rifle.  The measurement from there to the end of the permanently attached muzzle device is the length of the barrel.

HPD is not the ATF.
In registering hundreds of rifles, I've never seen them use a dowel.

All my ak's when registered at hpd were never measured with a dowel. They just hold it up against the window and there's a yard stick or ruler of some sort. All my barrels are 16.5 inches but on the registrations a few say 16.5 others are 17 and one is 18.