Some have said you can't take a firearm you recently bought to the range or travel with it, even though the transfer was completed, until it's registered.
Today, this was posted:
You're gonna have to register it before you can sell it
The FFL it is being sent to will not do the ATF paperwork for anyone other than the person who purchased it, HPD is sent an email as soon as the firearm is picked up notifying them of transfer from them to the purchaser. You can not do anything with the firearm except register it at that point. If it is sold to another party they are essentially recipient to an unregistered firearm. I've already had a similar situation come up like this and asked what to do. It cannot be transferred to another party until it is registered.
Sounds like you've done this before. I have not. But I think the state preventing the lawful commercial activities of a citizen (selling something he legally owns) is a real problem -- particularly since the process can take months to find a registration appointment.
Since it's legal to gift a firearm you bought at a dealer, as in you paid for it and someone else appeared to fill out the 4473, I find it unreasonable to delay a transfer for months to complete a process that has zero to do with the actual transfer process.