[marklbucla]

Suppose one has a registered pistol gripped shotgun AOW and puts on a regular stock set. Does it become a Short Barreled Shotgun or is it once an AOW, always an AOW?

[ugaarguy]

Without an 18" bbl it becomes an SBS, illegally as well unless the proper paper work is filed & approved, and appropriate taxes paid. Even with an 18" bbl & standard stock set the receiver is still registered as an AOW so I'm not sure if it's even legal to do.

Also, if it leaves the factory with a stock on it can't be registered as an AOW even with a pistol grip installed. Along this line if you were to legally convert your AOW shotgun to an SBS it would always be an SBS, even if reassembled to AOW form.

[wdlsguy]

Suppose one has a registered pistol gripped shotgun AOW and puts on a regular stock set. Does it become a Short Barreled Shotgun
It would become an unregistered short-barreled shotgun (very bad idea).

or is it once an AOW, always an AOW?
You could dispose of the < 18" barrel and ask BATFE to remove it from the NFA registry. It would revert to its previous classification (pistol grip only shotgun?).