Quoted:
Supressor question. Do you get the form 4 to purchase one? And how does this work? I assume they want the ser# on the form 4, so do you purchase and have it delivered to your dealer then send in the for four with the ser#? That would suck if you got denied! Or am I completely off base there?
Generally, you arrange with your dealer to buy a XXX suppressor, whether he has it in stock or will merely be your local transfer agent after you purchase it from a non-local vendor such as Major-Malfunction.com, etc.
If your local dealer has it in stock, you begin the Form 4 transfer process including the serial number for your can on the Form. Include your check and finger prints/photograph or LLC info. Wait. Profit!
If your dealer has yet to get the can or will merely be acting as your transfer agent (it's always polite to ask them first), then they must do a FOrm 3 transfer "Dealer To Dealer". Once he gets your can to him, then you can begin the above Form 4 process, but not before since you need the serial number.