There are a couple of possibilities for saving these guns if they were never registered. From ATF NFA handbook:
Section 2.4 Applications to remove firearms from the scope of the NFA as collector’s items. Certain NFA weapons can be removed from the provisions of the NFA as collector’s items. The procedures for requesting removal of an NFA firearm are the same as used for requesting a destructive
device determination. An NFA firearm removed from the NFA as a collector’s item is no longer subject to any of the provisions of the NFA. In most cases, the weapon will still be a firearm as defined in the GCA and
subject to regulation under the GCA. In some situations, the weapon that is removed from the NFA as an item will be an antique firearm as defined in the GCA.27 In these instances, the weapon would no longer be a firearm as defined in Federal law.
The Attorney General does not have the authority to remove a machinegun or a destructive device from the provisions of the NFA as collector’s items. Therefore, applications to remove machineguns or destructive devices from the NFA as collector’s items cannot be approved.
Section 2.5 Removal of firearms from the scope of the NFA by modification/elimination of components. Firearms, except machineguns and silencers, that are subject to the NFA fall within the various definitions due to specific features. If the particular feature that causes a firearm to be regulated by the NFA is eliminated or modified, the resulting weapon is no longer an NFA weapon.
For example, a shotgun with a barrel length of 15 inches is an NFA weapon. If the 15- inch barrel is removed and disposed of, the remaining firearm is not subject to the NFA because it has no barrel. Likewise, if the 15 inch barrel is modified by permanently attaching an extension such that the barrel
length is at least 18 inches and the overall length of the weapon is at least 26 inches, the modified firearm is not subject to the NFA. NOTE: an acceptable method for permanently installing a barrel extension is by gas or electric steel seam welding or the use of high temperature silver solder having a flow point of 1100 degrees Fahrenheit.
A shot pistol (“any other weapon”) such as an H&R Handy Gun may be removed from the NFA by either disposing of the smooth bore barrel or permanently installing a rifled sleeve chambered to accept a standard pistol cartridge into the smooth bore barrel. Modified by sleeving the barrel, an H&R Handy Gun is no longer an NFA weapon because it now has a rifled bore.
Large caliber destructive devices that are not also machineguns can be removed from the NFA by disposing of the barrel. If the barrel of a 37mm cannon is removed and disposed of, the remaining weapon has no barrel or bore diameter. As an alternative, the barrel of a destructive device may be
functionally destroyed. To destroy the barrel of a destructive device the following operations must be performed:
• Cut a hole, equal to the diameter of the bore, on a 90-degree angle to the axis of the bore, through one side of the barrel in the high pressure (chamber) area.
• Weld the barrel to the receiver of the weapon.
• Weld an obstruction into the barrel to prevent the introduction of a round of ammunition.
2.5.1 Removal of machineguns and silencers from the scope of the NFA. Machineguns are defined to include the receiver of a machinegun and the definition of silencer includes each component of a
silencer. Therefore, to remove these weapons from the provisions of the NFA, the receiver of a machinegun or all the components of a silencer must be destroyed. The preferred method for destroying a machinegun receiver is to completely sever the receiver in specified locations by means of a cutting torch that displaces at least one-quarter inch of material at each
cut location. ATF has published rulings concerning the preferred destruction of specific machineguns.
A machinegun receiver may also be properly destroyed by means of saw cutting and disposing of certain removed portions of the receiver. To ensure that the proposed saw cutting of a particular machinegun receiver is acceptable, FTB should be contacted for guidance and approval of any alternative destruction proposal. Note: a machinegun receiver that is not properly destroyed may still be classified as a machinegun, particularly in instances where the improperly destroyed receiver is possessed in
conjunction with other component parts for the weapon.
A silencer may be destroyed by completely severing each component by means of a cutting torch that has a tip of sufficient size to displace at least one-quarter inch of material at each cut location.
Concerning the outer tube(s) of a silencer, these components may be destroyed by crushing them flat in lieu of cutting with a torch.
Anyone interested in destroying an NFA weapon by means other than described above should contact FTB to discuss possible alternatives.
Also:
3.2.2 Registration by State and local agencies. To be lawfully possessed by States and political subdivisions of the States (for example, local police departments), NFA firearms must be registered in the NFRTR. The regulations permit State and local police organizations acquiring unregistered NFA
firearms for official use, by seizure, forfeiture, or abandonment, to register them in the NFRTR by filing ATF Forms 10. Appendix C contains a copy of the form. Firearms registered on Forms 10 are for official use only and subsequent transfers will be approved only to other government agencies for official use. For example, they may not be traded to an FFL/SOT in exchange for other firearms or police equipment.
Certain museums are allowed to have NFA weapons registered on a Form 10 in their collections. It ain't much but it beats just completely melting them down.
Traded it on a Cutlass as soon as the warranty expired to avoid the repair bills.