Much more hereThe Washington Times wrote:Gun makers baffled by ATF criteria
Models OK’d on case-by-case basis
The Bureau of Alcohol, Tobacco, Firearms and Explosives is in charge of determining whether a gun model is legal, but the agency won’t say much about its criteria.
Despite overseeing an industry that includes machine guns and other deadly weapons, ATF regulations for the manufacture of weapons are often unclear, leading to reliance on a secretive system by which firearms manufacturers can submit proposed weapons for testing and find out one at a time whether they comply with the law, critics say.
The ATF recommends that manufacturers voluntarily submit weapons for case-by-case determination. But those judgments are private and, it turns out, sometimes contradictory. Critics say nearly identical prototypes can be approved for one manufacturer but denied for another.
The article lists multiple instances of manufacturers starting production based on an ATF opinion letter that green lights their design, then the ATF reverses itself leaving them with a half million in unusable inventory.
ATF has no rules, except those they make up on the fly to suit whatever executive decision they want to promote. Look at Elite Ammunition or Cav Arms! Ask ATF if doing X is OK, and they send an official letter saying YES, it is... then a year or two later they change their mind, don't inform you, but send in the shock and awe stormtroopers to serve a warrant and kick in your office and seize all your inventory.
In these sort of things, perhaps an open discussion with the manufacturer FIRST and explain the situation "Hey, we reconsidered, we're going to issue a change of opinion, might want to go ahead and be ready for the announced change by being compliant in advance."
I guess that might be too much to ask. Sensibility from the BAT-Fers.
Here is a perfect example of the above:
The original ruling:


Now the reversal:

The whole "AP ammo" is a ridiculous law anyway. If a criminal wants to defeat a vest, they aren't going to use an FN Five-seveN pistol anyway when virtually any decent rifle caliber will zip though an ordinary vest like butter.
If we get tired of discussing Barnes Banded Solid bullets, how about shoestrings that are a "machine gun"?