6.5 Grendel barrel Length?????

[lazyengineer]

"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.

It would seem that everyone everywhere including the ATF, would disagree with you.

The stripped lower is essentially a part. When you configure that non-fire-able part alone, as a rifle or as a pistol, you have now made it into an actual functional firearm, in the form of a rifle or a pistol, and you did so with intent and by design. Once it first becomes a rifle or a pistol, that is what it becomes. Once it's a pistol, putting a longer barrel on that pistol, so that it is more than 16", makes that pistol still a pistol, but a pistol with a really long barrel, that you can now put a stock on, as there is no regulation saying you can't put a stock on a pistol, only that the boom-stick can't be <16", if it has a stock. It looks like a rifle, we say "rifle", but it's a pistol with a stock and a long barrel. It's still a pistol. Hence the ability to go back and forth easily, it never stopped being a pistol.

If it first is made into a rifle, it's a rifle, by intent and design when you did that. And once it's a rifle, you cannot put a <16" Barrel on it, as a rifle can never have a <16" barrel; and so you made it into a different classification of a firearm (hence their last sentence in first paragraph, saying doing so makes a new firearm), and it it is now a short barreled rifle.

That's the symantics behind the at-first-glance seemingly goofy rulings on pistol to "rifle" back to pistol OK, but Rifle to Pistol is not.