Does a permently attached muzzle nut count as a muzzle attachment in relation to the U.S. parts count? I plan on having a milled AK with the early style nut (as opposed to the slant brake)built. So would I only need 4 U.S. parts instead of 5?

Tracking ATF interpretations is no fun. It would be my choice to consider that the nut serves no other purpose than to cover the threads at the end of the muzzle (complying with other laws), so it is neither a bbl extension or muzzle attachment. But then again I do not have any guns so equipped in my inventory.
You can also go to aft.gov and just ask them by e-mail for a clarification.


[Code of Federal Regulations]
[Title 27, Volume 1]
[Revised as of April 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 27CFR178.39]

[Page 1149]

           TITLE 27--ALCOHOL, TOBACCO PRODUCTS AND FIREARMS

CHAPTER I--BUREAU OF ALCOHOL, TOBACCO AND FIREARMS, DEPARTMENT OF THE
                               TREASURY

PART 178--COMMERCE IN FIREARMS AND AMMUNITION--Table of Contents

        Subpart C--Administrative and Miscellaneous Provisions

Sec. 178.39  Assembly of semiautomatic rifles or shotguns.

   (a) No person shall assemble a semiautomatic rifle or any shotgun
using more than 10 of the imported parts listed in paragraph (c) of this
section if the assembled firearm is prohibited from importation under
section 925(d)(3) as not being particularly suitable for or readily
adaptable to sporting purposes.
   (b) The provisions of this section shall not apply to:
   (1) The assembly of such rifle or shotgun for sale or distribution
by a licensed manufacturer to the United States or any department or
agency thereof or to any State or any department, agency, or political
subdivision thereof; or
   (2) The assembly of such rifle or shotgun for the purposes of
testing or experimentation authorized by the Director under the
provisions of Sec. 178.151; or
   (3) The repair of any rifle or shotgun which had been imported into
or assembled in the United States prior to November 30, 1990, or the
replacement of any part of such firearm.
   (c) For purposes of this section, the term imported parts are:
(1) Frames, receivers, receiver castings, forgings or stampings
(2) Barrels
(3) Barrel extensions
(4) Mounting blocks (trunions)
(5) Muzzle attachments
(6) Bolts
(7) Bolt carriers
(8) Operating rods
(9) Gas pistons
(10) Trigger housings
(11) Triggers
(12) Hammers
(13) Sears
(14) Disconnectors
(15) Buttstocks
(16) Pistol grips
(17) Forearms, handguards
(18) Magazine bodies
(19) Followers
(20) Floorplates

[T.D. ATF-346, 58 FR 40589, July 29, 1993]

[[Page 1150]]

No, the brake does not count towards your final tally. I'll break it down easily:

STAMPED w/foreign brake/nut needs 6 US parts
STAMPED w/US or no brake/nut needs 5 US parts

MILLED w/foreign brake/nut needs 5 US parts
MILLED w/US or no brake/nut needs 4 US parts

But to specifically answer your question, I would like to play the role of ATF moderator here by suggesting this:

Take for example you have an Romanian AK-74 with Romanian FSB and 22mm brake like a CampyClone...

Prior to the ATF letter that has been around for some time now, we had to permanently install this 22mm brake, and at the same time a 6th US part was needed to remain compliant due to the addition of the foreign brake.

IMO, this suggests that even though it was permanently installed, it does NOT make it a barrel extension, but rather is still considered an additional part even though it will never come off.

So unless you find a US made muzzle nut, I think you will need 5 US parts in the milled rifle regardless of whether it is permanently attched or not(though it needs to be permanent anyway for legality...)