6.5 Grendel barrel Length?????

[depletedyourcranium]

Might want to read that letter again. First paragraph in italics is clear. Converting a pistol via attaching parts (in our example an upper), that make it into a rifle, is not making a new firearm. Converting a rifle that was originally intended to be a rifle, into a pistol, IS making a new firearm.

"assembled or produced from a weapon
originally assembled or produced only as a rifle."

A stripped lower receiver does not meet this definition. A stripped lower is transferred as a "firearm", and is never originally produced as only a rifle. It does not matter which order the end user configures the firearm as. The receiver leaves the manufacturer a serialized "firearm", not only a rifle.

Not that the BATFE makes much sense with some or most of their rulings, but it seems incredibly arbitrary to say if you first build out a stripped lower into a rifle, it's a rifle forever, but that if you build it first as a pistol, then you can go back and forth from pistol to rifle forever. I don't read this in the letter and don't think that applies to their wording as we extrapolate it out to AR15 lowers.