The following is a hypothetical question, but I would appreciate if anyone has real world examples of guns like this that might apply. My question has to do with federal law, not any particular state law, so no CA, MI, NY, etc. specifics apply.
Imagine a bullpup rifle with a 16.5" barrel.
The bullpup rifle has an extendable telescoping stock which is continuously adjustable.
When the stock is fully extended, the rifle is 26.5" length from the muzzle crown to the stock end along a line parallel to the bore. When the stock is fully collapsed, the gun OAL is only 22".
The rifle can be fired when the stock is fully extended, fully collapsed, and anywhere in between.
Am I correct in assuming that this gun is NOT a short-barreled rifle (according to federal laws)? If not, why not?