Yes, it is. And I believe it is unconstitutional. They have background checks to find out if you are a “prohibited person” and if you are not deemed so then it shouldn’t matter to them what particular firearm you purchase.
It shouldn’t, but as a former FFL holder, I got a call about a Colt Python. 1 number out of 5 was readable. Had be used in an armed robbery (rich crook apparently). The FBI called @ 0600 one AM looking for the name of the guy I sold it to. I called the guy to make sure he still had it. They had tracked at least 19999 Pythons to the seller in under 24 hours.