Because of this, the SUPER-SHORTY is considered an AOW (Any Other Weapon) and can be transferred with a $5 stamp!
I think even with the conversion its still not a 200.00 stamp.

I could be wrong. The best NFA person in town is probably Greg @ Denver Bullet. He could tell you what you'd need to do. And no, even with the shortening, Mossy 5xx's are notoriously poor about feeding shorter than standard shells.