National Does Counterbore Diameter Count As Bore Diameter When ATF Is Measuring For 50cal + Bores.

[arakboss]

Imagine I have a 50 Beowulf Rifle with 20" barrel that I counterbored .520 diameter by .250 deep to eliminate a worn crown. If the ATF were to measure my bore to see if it exceeds .500, would they measure only the rifled part of the barrel or would they also measure the counterbore diameter? If they measured the counterbore, would they shoot my pup?

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[VinnieBoomBah]

It all counts, from breach face to end of the barrel, if it didn't then pin & welding a flash hider wouldn't work, but it does.

 

[arakboss]

It all counts, from breach face to end of the barrel, if it didn't then pin & welding a flash hider wouldn't work, but it does.

That was going to be my guess but I couldn't find any info to back it up.

 

[edzz]

I would go with the point of most resistance.
Story of my life...

I agree with the pin and weld comparison.

 

[bcp]

From:

https://www.atf.gov/firearms/docs/undefined/atf-national-firearms-act-handbook-chapter-2/download

"The ATF procedure for measuring barrel length is to measure from the closed bolt (or breech-face) to
the furthermost end of the barrel or permanently attached muzzle device. Permanent methods of
attachment include full-fusion gas or electric steel-seam welding, high-temperature (1100°F) silver
soldering, or blind pinning with the pin head welded over. 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furthermost end of the barrel or permanently attached muzzle device, withdrawn from the barrel, and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."


Bruce

 

[red442joe]

He is not asking about length.

Joe

 

[JuglansRegia]

It shouldn't matter but when dealing with a government agency, common sence does not apply. You are following the spirit of the law since your projectile is still not over .5"

 

[red442joe]

Here, try this: https://www.thehighroad.org/index.php?threads/how-is-the-50-bore-limit-measured-by-the-atf.571174/

Joe

 

[red442joe]

For a rifle, it appears the BATFeces turds measure from the top of the lands, as opposed to the bottom of the grooves.
A muzzle device is just that, a muzzle device, not a "bore", but W.D.I.K. The best answer to how does ATF do anything? Arbitrarily.

Joe

 

[bcp]

From:

Firearms - Guides - Importation & Verification of Firearms - National Firearms Act Definitions - Destructive Device | Bureau of Alcohol, Tobacco, Firearms and Explosives

Previous Page Download this Section Download the Guidebook

www.atf.gov

For the purposes of the National Firearms Act, the term "Destructive Device" means:
...
Any type of weapon by whatever name known which will, or which may readily be converted to expel a projectile, by the action of an explosive or other propellant, the barrel or barrels of which have a bore greater than one-half inch in diameter.

Exemptions:
...
a rifle which the owner intended to use solely for sporting purposes.

Bruce

 

[arakboss]

It all counts, from breach face to end of the barrel, if it didn't then pin & welding a flash hider wouldn't work, but it does.

I gave this more thought and have to respectively disagree that bore measurement is considered all the way down to the breech. The exterior diameter of the 50 Beowulf case is well over .500. If they dropped a .500 pin in the 50 Beowulf chamber, it would swallow the pin. I suspect other chambers would as well.

That makes me wonder if they only measure the rifled portion of the bore?

 

[arakboss]

If the atf included bores of pin and welded muzzle devices in their measurements, it seems like many muzzle devices would measure over .500, even an A2 flash hider, I'll bet?

 

[VinnieBoomBah]

I gave this more thought and have to respectively disagree that bore measurement is considered all the way down to the breech. The exterior diameter of the 50 Beowulf case is well over .500. If they dropped a .500 pin in the 50 Beowulf chamber, it would swallow the pin. I suspect other chambers would as well.

That makes me wonder if they only measure the rifled portion of the bore?

Yeah, I misread the 'bore' part

 

[red442joe]

I gave this more thought and have to respectively disagree that bore measurement is considered all the way down to the breech. The exterior diameter of the 50 Beowulf case is well over .500. If they dropped a .500 pin in the 50 Beowulf chamber, it would swallow the pin. I suspect other chambers would as well.

That makes me wonder if they only measure the rifled portion of the bore?

This...
And...

 

[red442joe]

If the atf included bores of pin and welded muzzle devices in their measurements, it seems like many muzzle devices would measure over .500, even an A2 flash hider, I'll bet?

This.

Joe

 

[red442joe]

Just guessing, 'cuz the BATFeces turds will do what they want....
The bore is measured at the rifled part.
With a rifled choke in a shotgun....it will not be a rifle, because of removeability, and will have to maintain 18" barrel.
A 410, non removeable full choke, that gets the full choke zone rifled, would be a rifle, however.....I personally would maintain 18" of barrel to be safe(from the BATFeces turds).
I wouldn't cut down to 16", which would lose the choke zone anyway.

Joe

 

[spookshack]

No, he's

He is not asking about length.

Joe

No, he is asking about girth…..

 

[Xaevian]

No, he's

No, he is asking about girth…..

It think that is stretching it.

 

[red442joe]

It think that is stretching it.

Gretchen can take it.

Joe