[jdanp]

There’s no law banning the “stockpiling” of weapons in any locale of the United States or at the federal level. You can own hundreds of rifles, shotguns, and handguns even in places like NYC as long as you purchase/possess/register the guns in accordance with all local laws.

[patagonia]

I should have said "effectively". There is no law saying that explicitly, however, try stockpiling 1000 weapons of the same sort in a manner not meant to be difficult to be noticed and see how long it takes for you to be on someones radar.