Actually, the Attorney General, one Homer S. Cummings, and the FDR administration proposed a sliding transfer tax that was intended to be prohibitory. IIRC, the transfer tax was $5000 on a machinegun, $2000 on a handgun, $1000 on a rifle and $500 on a shotgun. In addition, there would be a tax of $50 on each round of handgun ammo, $20 on each round of rifle ammo, $5 on each shotshell, and $.50 on each round of .22 ammo. Multiply by around $40 for today's dollar values.
All guns had to be registered and no inheritance would be allowed. But NOTE, as Sen. Obama emphasizes, no one would TAKE AWAY any guns. Until you die, then into the furnace went your guns.
When Congress got done in 1934, the bill was watered down to what is essentially the NFA as it exists today as part of GCA '68.
Also note well that while his attorney general was pushing what would effectively be a ban on guns, FDR was claiming to be a "hunter and sportsman" even having himself decked out in a shooting jacket and carried to the firing line of a military rifle range where he held a Model 1903 like he had never seen one before, which he probably hadn't. Sound familiar?
Jim