18" should be 18".
If it comes up right on the money 18.0 with a steel tape, there is a chance someone else's tape will read a smidge different.
Those 1/2" blade homeowners tapes are not that precise. Its just a printed film stretched over a steel blade with a wiggly end that may or may not be in good shape or properly attached. You also are aware that a lot of folks, including law enforcement officers, do not know where to take the measurement. I have gotten at least one shotgun cheep at a farm auction ($5.00) because the potential bidders thought it was too short. It was well inbounds, and I checked with a tape on the table next to it before bidding.
Between inaccurate tapes and ignorance of correct measuring protocol, most folks don't go below 18 1/2.
That 1/2 inch is very inexpensive insurance.
If accuracy of the barrel measurement is the question:
A rod inserted against the bolt face and marked with a razor knife resting on the muzzle is a good way to gage it.
(A calibrated depth micrometer would be better, but who has one)
Then you can put the gage against an engraved steel rule of known accuracy and get a good number.
Alternately, measure it with several tapes and start at 10 inches.
That gets you out of the numbers worn from years of use and any end play error in hook.
Using several tapes will average out the instrument error.
As a practical matter
If the barrel is too short:
The cash value of a sawed off shotgun is much much less than the potential fines, legal fees and lost income from prison time.
I suspect the sentimental value will also go way down if you get fitted with a set of chrome bracelets.
The risk to reward equation does not make sense to me.
Its possible to add a "permanently attached muzzle device", but you better know what that means before trying it.
My poor understanding of that topic is soft solder and epoxy are generally not considered "permanent".
If its a common gun, and you can find a barrel, that's a better choice, and probably less effort.
Form 1, isn't that supposed to be done prior to construction?
I have not gone down that road, so I am not sure, and I would not want to make a mistake in that area.
The safest route is disassemble it.
Crush the noncompliant barrel.
Replace the barrel with a legal one and move on.
Also, check the overall length, I forget the exact number, but if its a pistol grip brake open, its easy to get below the overall legal with a compliant barrel length. If you have traditional stock on a pump or auto loader, your probably ok on overall length.
If it comes up right on the money 18.0 with a steel tape, there is a chance someone else's tape will read a smidge different.
Those 1/2" blade homeowners tapes are not that precise. Its just a printed film stretched over a steel blade with a wiggly end that may or may not be in good shape or properly attached. You also are aware that a lot of folks, including law enforcement officers, do not know where to take the measurement. I have gotten at least one shotgun cheep at a farm auction ($5.00) because the potential bidders thought it was too short. It was well inbounds, and I checked with a tape on the table next to it before bidding.
Between inaccurate tapes and ignorance of correct measuring protocol, most folks don't go below 18 1/2.
That 1/2 inch is very inexpensive insurance.
If accuracy of the barrel measurement is the question:
A rod inserted against the bolt face and marked with a razor knife resting on the muzzle is a good way to gage it.
(A calibrated depth micrometer would be better, but who has one)
Then you can put the gage against an engraved steel rule of known accuracy and get a good number.
Alternately, measure it with several tapes and start at 10 inches.
That gets you out of the numbers worn from years of use and any end play error in hook.
Using several tapes will average out the instrument error.
As a practical matter
If the barrel is too short:
The cash value of a sawed off shotgun is much much less than the potential fines, legal fees and lost income from prison time.
I suspect the sentimental value will also go way down if you get fitted with a set of chrome bracelets.
The risk to reward equation does not make sense to me.
Its possible to add a "permanently attached muzzle device", but you better know what that means before trying it.
My poor understanding of that topic is soft solder and epoxy are generally not considered "permanent".
If its a common gun, and you can find a barrel, that's a better choice, and probably less effort.
Form 1, isn't that supposed to be done prior to construction?
I have not gone down that road, so I am not sure, and I would not want to make a mistake in that area.
The safest route is disassemble it.
Crush the noncompliant barrel.
Replace the barrel with a legal one and move on.
Also, check the overall length, I forget the exact number, but if its a pistol grip brake open, its easy to get below the overall legal with a compliant barrel length. If you have traditional stock on a pump or auto loader, your probably ok on overall length.
