A morning news show included an interview with folks amazed that the San Bernardino shooters had accumulated so much ammunition, explosives, etc. How did no one notice them accumulating this deadly stuff?
We had this problem a few years back with people buying large quantities of pseudoephedrine to cook meth. Now quantities of cold medicines including this drug get dispensed from behind the pharmacy counter. You must show identification to purchase, and your purchase gets logged in a database to keep you from going store to store. Other cold medications also require ID at checkout, even though they are not sequestered behind the counter (and I am not certain how you would make them into a drug with street value).
We could do something similar with ammunition. Yes, the vast number of bullets are sold to law-abiding citizens who would then be subject to government scrutiny. Of course, the same is true of pseudoephedrine, but we are willing to take a chance with a bit of liberty for the public good.
I'm up for it for bullets.
I'm sure that this idea will get as far as extended background checks for gun purchases and banning those on the no-fly list from gun ownership (really? people can't get on a plane, but it's safe for them to have a firearm?!?).