Buy rifle (you need the Serial on the receiver)
Pay stamp
Get stamp back
engrave
cut barrel.
If not buying a full rifle it doesnt matter. All you need to know is that you need the receiver w/ the serial. That goes on your paperwork. Fill out your forms and send off with your check. Wait for it to come back, then get the receiver engraved. Then "build" the SB part of the SBR. (if building from parts, make sure your barrel is at least the minimum for standard rifle until you get a stamp back)
If you bought a Noveske 10.5 (full rifle), it would be under a Form 4.
I think you purchase the rifle, which has to be transfered to a c3 dealer in your area, then the paper work is filled out and sent. Once received (form approved/stamp), your local C3 dealer would release it to you.
I could be wrong. I've never form4ed a full rifle that wasnt "built" by my local C3.