Quoted:
It says on a form 3, so it is dealer sample and so you'd have to have an FFL and SOT stamp to even consider it. However, at that price, you could get your FFL and pay the $500 SOT tax and still maybe come out ahead...
FAIL!
It's an SBR. If it is in a dealer's inventory, it can transfer tax-free to another dealer. A Form 3 is used for this.
If an NFA firearm transfers to or from a non-SOT, it would need to be taxed, and this is typically done with a Form 4. So it could go to an individual in Missouri using a tax paid Form 4 and they could pick it up directly from CMMG. Or if someone in another state wanted to buy it, it would transfer tax free to their dealer using a Form 3, and then to the individual using a Form 4.
So yes - an individual can buy that gun.