NFA experts: IS this shotgun a SBS?

[Cochese]

I have a 1960's vintage Westernfield M550A, aka Mossberg 500. It was put into service at a police department after having its 24" turkey barrel cut down, presumably by a smith, since the cut is clean appears to function as it should.

My problem is its size. I have some pictures to explain my ramblings. When the gun is assembled, measuring from the end of the receiver to the end of the barrel, it is 17.5"...





You can see the wear line I am measuring from.



This is the same measuring line with the barrel removed:



This is what the receiver side of the barrel looks like:

It has a short and long side.



Measuring from the long side to the end of the barrel, uninstalled, it is 19.5"



From the "short" side of the receiver end to the barrel end it is 18.5"





My question is:

Which is the legal way to determine the barrel length?

Like this, at 18.5"



Or from the end of the receiver where the barrel is exposed as indicated by the wear ring on the barrel:



17.5"

[Irving]

That's a great question and I'm interested to hear the answer.

[SA Friday]

If I remember correctly, there's actually two measurements for a SBS; one for the barrel and one for the overall length. They both have to be in compliance.

It's a good question though. I have no idea on the exact locations for the measurements.

[ChunkyMonkey]

Under the National Firearms Act (NFA) it is illegal for a private citizen to possess a sawed-off modern smokeless powder shotgun (a barrel length less than 18 in. or 46 cm and an overall length less than 26 inches) without a tax-stamped permit from the Bureau of Alcohol, Tobacco, Firearms and Explosives, which requires a background check and a $200.00 fee for every transfer

Yours seems to be shorter.

[Not_A_Llama]

Drop a dowel down the bore with the bolt forward. Make a mark on the dowel at the muzzle.

IIRC, that's the official way.

Shotgun also has to be 26" overall.

This post not to be construed as legal advice.

[The Extractor]

that is stupid, why would legal shotguns and rifle bbl length
requirements be 2 inches different ?

[Jai]

You measured from the right place. 26 over all, 18 barrel, if there is a flash suppresor or compensator that is hand removable you take that off for the messurement.

[Irving]

It's the BATFE, that's why.

[The Extractor]

that was kind of a rhetorical question....

[roberth]

Drop a dowel down the bore with the bolt forward. Make a mark on the dowel at the muzzle.

IIRC, that's the official way.

Shotgun also has to be 26" overall.

This post not to be construed as legal advice.

IIRC this is what I was told as well.

These are stupid rules that only apply to law abiding citizens. I would like to see the GCA 1934, 1968, and 1986 repealed and start punishing criminals.