U.S. Department of Justice
Bureau of Alcohol. Tobacco, Firearms and Explosives



903050:MSK 3111/2006-583


APR 2 02006
Mr.

Dear Mr.'
This refers to your correspondence dated March 15, 2006, to the Firearms Technology Branch (FTB), Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), which accompanied your submitted barrel retaining system and related components. In your letter, you seek guidance regarding this retaining system, which you have designed for a semiautomatic version of a Suomi M31 machinegun. Specifically, you want to ensure that the finished weapon incorporating this system will not be classified as a "short barreled rifle" (SBR) under the National Firearms Act (NFA).
For your information, the National Firearms Act (NFA), 26 U.S.C. Section 5845(b), defines a "machinegun" as follows:
...any weapon which shoots, is designed to shoot, or can be readily restored to shoot,
automatically more than one shot, without manual reloading, by a single function of the trigger. The term shall also include the frame or receiver of any such weapon, any part designed and intended solely and exclusively, or combination of parts designed and intended, for use in converting a weapon into a machinegun, and any combination of parts from which a machinegun can be assembled if such parts are in the possession or under the control of a person.
In addition, the NFA, 26 U.S.C. 5845(a)(3), defines "firearm," in part, as ...a rifle having a barrel or barrels of less than 16 inches in length....
Finally, the GCA, 18 U.S.C. Section 922(r), prohibits assembly of certain semiautomatic rifles and shotguns from imported parts. The implementing regulation, 27 CFR Section 478.39, includes the stipulation that no person shall assemble a semiautomatic rifle or any shotgun using 10 or more of certain imported parts, if the assembled firearm is prohibited from importation under 18 U.S.C, Section 925(d)(3) as not being particularly suitable for or readily adaptable to sporting purposes.

The FTB examination of the barrel retaining system (or mounting block), barrel, and barrel shroud that you have sent us reveals that your proposed weapon will have a newly manufactured barrel which is approximately 17 inches in length.
Also, your newly manufactured system (mounting block) has been redesigned to preclude the mounting of a standard Suomi M31 machinegun barrel.
A weapon incorporating your newly designed barrel retaining system (mounting block) and a barrel with a length of 16 inches or more would not meet the definition of an SBR and would not be a "firearm" as defined in 26 U.S.C. 5845(a)(3).
With respect to designing your semiautomatic version of the Suomi M31 machinegun, we advise you to consider incorporating the following features and specifications:
1.        The receiver should be of substantially smaller diameter than a standard
Suomi sub-machinegun receiver to preclude the use of an unmodified Suomi machinegun bolt.
2.       A steel rail should be installed in the receiver to prevent use of fully
automatic bolts. The rail should be installed in the receiver by a secure, full-fusion seam weld.
3.        The feed lips should be eliminated from the bolt.
4.        An open-bolt firing mechanism with a fixed firing pin must not be used.
5.        A hammer or striker mechanism incorporating a positive semiautomatic disconnector should be used.
6.        The sear mechanism and opening should be relocated or modified so that a standard Suomi sear mechanism cannot be introduced into the weapon.
7.       The firing mechanism should be designed to use an inertial striker (firing pin).
Since a semiautomatic version of the Suomi M31 would be prohibited from importation under Section 925(d)(3), the requirements listed above under 18 U.S.C. Section 922(r) would apply to the rifle you propose to build.

-3-Mr,
Once assembled, the rifle must not contain more than 10 of the following parts that are obtained as imports:
(1) Frames, receivers, receiver     (11) Triggers,
castings, forgings, or castings.     (12) Hammers.
(2) Barrels.     (13) Sears.
(3) Barrel extensions.     (14) Disconnectors.
(4) Mounting blocks (trunnions).     (15) Buttstocks.
(5) Muzzle attachments.     (16) Pistol grips.
(6) Bolts.     (17) Forearms, handguards.
(7) Bolt carriers.     (18) Magazine bodies.
(8) Operating rods.     (19) Followers.
(9) Gas pistons.     (20) Floorplates.
(10) Trigger housings.
We suggest that as soon as you have completed your semiautomatic Suomi M31, incorporating the design features described above, you submit it to FTB for a determination. Without actually examining a sample, our Branch is unable to make a formal classification of the manufactured firearm. After the evaluation, we would provide you with a classification letter.
The weapon would be returned unless FTB found that it constituted a violation of the NFA or other Federal firearms laws.
Finally, due to the possibility that making and possessing any such firearm may also be prohibited under State law or local ordinances, we advise you to contact local law enforcement authorities for further information.
To facilitate return of the current sample you have sent to FTB, please provide our Branch with an appropriate FedEx or similar account number within 60 days of receipt of this letter.
We thank you for your inquiry and trust the foregoing has been responsive to your request for guidance and an evaluation.

Sterling Nixon Chief, Firearms Technology Branch
Sincerely yours,