ATF SBR Measurement Precision


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carnaby
August 6, 2011, 12:20 AM
Surfing the web and had a thought after reading ATF documentation on their measurement procedure for the determination of the classification of a rifle as an NFA SBR or not...

To what precision does the ATF make this measurement? Their docs say:

Barrels are measured by inserting a dowel rod into the barrel until the rod stops against the bolt or breech-face. The rod is then marked at the furthermost end of the barrel or permanently attached muzzle device, withdrawn from the barrel, and measured.

The text in red has me concerned. Suppose I build an AR15 upper that when marked and measured with 0.01" precision comes out exactly 16.0". Will the ATF make the measurement with the same care? Is it feasible that they could make a measurement with 0.1" precision and come out 15.95"? If that happened would I be in trouble, or would they acknowledge that it's within reasonable measurement precision and not worry about it?

How close is close enough to be safe and certain one won't run afoul of the law?

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medalguy
August 6, 2011, 12:54 AM
That's why most folks go 16 1/2 inches, just to be on the safe side.

carnaby
August 6, 2011, 05:39 PM
Right, but is it really necessary to be on the safe side?

tarosean
August 6, 2011, 05:46 PM
^^^^Club Fed or a half an inch??? I know which one I would choose..

Sam1911
August 6, 2011, 05:58 PM
If you were ever arrested and charged for such a violation, you would certainly be able to have at your disposal the very best experts you could afford. Surely it wouldn't be difficult to provide your defense team with a tape measure capable of measuring at least to the 1/16". :)

Seriously, a measurement of length is a pretty finite thing. You can dial up the precision to whatever level you want. At some point it is either greater than 16" or less than 16". If that is 16.0000000001" you're in the clear. (Arguably, if it is 15.999999999998, then you aren't, but I can't imagine they'd go to those lengths to get that conviction, or be able to successfully prosecute you for being millionths of an inch under.) They can't prosecute you for a gun that actually does meet the required standard.

Getting your case tossed out because they measured sloppily would be the easiest legal defense of all time.

tarosean
August 6, 2011, 06:18 PM
Getting your case tossed out because they measured sloppily would be the easiest legal defense of all time.

Before or after paying the equivalent cost of a real SBR or two and Tax stamps to the Attorneys? :)

Iramo94
August 6, 2011, 07:07 PM
Before or after paying the equivalent cost of a real SBR or two and Tax stamps to the Attorneys?
If your barrel really is the correct length, you wouldn't even need a lawyer. Just inform the judge that you are "acting pro se" (http://www.jud.ct.gov/faq/represent.html) and then break out the micrometer. Ten minutes and a few pages of paperwork later, you're on your way home.

Jim K
August 6, 2011, 08:36 PM
Sounds great, Iramo. Have you ever done that or have personal knowledge of someone who has? It has been said, with a lot of truth, that a person who defends himself has a fool for a client. (And where do you get a 16" micrometer.)

As to cost, even getting a defense attorney to show up will cost a lot more than a couple of tax stamps unless you qualify for a public "defender".

Realistically, I doubt ATF would make an arrest based on .001" or that any U.S. Attorney would even think of taking such a case to trial. More likely the gun would be "taken for investigation" (confiscated) and the owner told to go home and don't be a wiseass.

BTW, when considering the legal possibilities of being a wiseass just to tweak the cops, remember that a bail bondsman wants 10% of the bond amount as his non-refundable fee. So if bail is $50,000 (light on a weapons charge), somebody better come up with five grand they will never see again or the accused gets to sit in jail thinking about that .001 inch.

Jim

carnaby
August 6, 2011, 11:47 PM
So nobody really knows. Best thing is to probably ask the ATF directly.

medalguy
August 7, 2011, 12:39 AM
May not be correct, but I was told by a friend who was an ATF agent MANY years ago (1960's) that they had a calibrated rod 16.000 inches long that they would drop down a barrel, then pass a straight edge across the end of the muzzle. If the straight edge touched any part of the rod, they considered the barrel long enough. If the straight edge passed freely with no contact, it was too short.

It's probably not BATFE that you need to worry about. It's probably the bubba deputy sheriff that will stop you on the way back from the range and think your barrel is too short. If you are lucky he MAY have an old Craftsman tape measure in the trunk of his car to use, probably not. He'll just take you in and things generally go south pretty quick after that. As the old saying goes, you can beat the rap but you won't beat the ride. And the expense. How long would you want to stay in jail before posting bond? They don't really care if you are there overnight or a week if they think your barrel is too short. Is it really worth it?

FIVETWOSEVEN
August 7, 2011, 01:19 PM
I believe you have it the other way around with that measuring rod.

Realistically, I doubt ATF would make an arrest based on .001" or that any U.S. Attorney would even think of taking such a case to trial. More likely the gun would be "taken for investigation" (confiscated) and the owner told to go home and don't be a wiseass.

I'm pretty sure this is what would happen more than anything for a case like this.

As the old saying goes, you can beat the rap but you won't beat the ride.

I say, safe in court doesn't mean safe on the streets.

Jim Watson
August 7, 2011, 03:21 PM
Is it feasible that they could make a measurement with 0.1" precision and come out 15.95"? If that happened would I be in trouble,

Yes.
The Weaver case that concluded with federal agents shooting people at Ruby Ridge started over a .25" shortfall in barrel length.
I think you would be prosecuted for .05" if they measured that closely.
Or at least the gun judicially stolen per fivetwoseven above.

WNTFW
August 7, 2011, 03:52 PM
Medalguy,
This: "May not be correct, but I was told by a friend who was an ATF agent MANY years ago (1960's) that they had a calibrated rod 16.000 inches long that they would drop down a barrel, then pass a straight edge across the end of the muzzle. If the straight edge touched any part of the rod, they considered the barrel long enough. If the straight edge passed freely with no contact, it was too short."

Sounds backwards.

waidmann
August 7, 2011, 07:08 PM
Jim K pretty well nailed it. BATF comes in two flavors, Investigators (compliance inspectors) and Special Agents (cops). If you are not involved in activities with non-nice people (and Randy Weaver sort of was) or if the piece is not in an inspectable premisis no one will take notice unless someone i.e. that local cop, your estranged wife or some thug acquaintance calls attention to you.
The BATF will have to take what they have to an Asst. U.S. Attorney and sell criminal intent to them. A silly 1/10th of an inch is cheap insurance. A longer appliance spot welded can corrrect most mistakes.

ants
August 7, 2011, 07:09 PM
they had a calibrated rod 16.000 inches "Calibrated" at what ambient temperature?



Dear brothers, at such level of precision (including the OP suggestion of 0.01 inches)
every degree Centigrade blows your dimension right out of the water.

Jim K
August 7, 2011, 08:43 PM
Above, I wrote, "Realistically, I doubt ATF would make an arrest based on .001" or that any U.S. Attorney would even think of taking such a case to trial. More likely the gun would be "taken for investigation" (confiscated) and the owner told to go home and don't be a wiseass."

I will now add that anyone who deliberately cuts a barrel to 16.001 inches is not simply complying with the law, he is playing games with the law, and is probably a legalistic, arrogant and nasty SOB as well. I don't think I want to know him.

Jim

medalguy
August 9, 2011, 05:31 PM
Correct, if the straight edge touched the rod, then it was too short. My bad. No idea how they calibrated the rod, probably at ambient temperature. I vaguely recall us discussing this, and it was about 50 years ago.

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