Can a VFG be added to a TAC-14 without becoming a NFA item? Something similar to the folding type you see on the Serbs Shorty models.

Good question.  It’s not a pistol, so it would reason that a VFG is allowed. The foreend is already a forward grip in every sense of the word.

That would be an AOW

When this thread wasn’t moving so well I started checking a few other places and some that made the explanation of AOW more clear. So because the TAC-14 is considered a “Firearm” and it’s over 26” a  VFG is fine just as a AR15 with a full length pistol buffer tube and a 11 1/2” barrel can have a VFG as it’s length is over 26”. Now make any changes that will bring the length to under 26” and it becomes a AOW.

Now to make things even crazier Remington now sells this over the counter.
https://www.remington.com/other-products/model-870-tac-14-arm-brace

So add a brace, cut the barrel ever further so long as the oal is >26"?

I just picked up a Mossberg Shockwave and was curious about this as well. I don't see an issue purely from the >26" standpoint.