The other aspect of this is that using the list to restrict weapons sales is a solution in search of a problem (in an odd way, not unlike the “voter ID” efforts of the Republicans). Is there any evidence that anyone who’s on the watch list has ever legally purchased a firearm, to say nothing of using it to kill anyone? Has any mass shooter in U.S. history been on the watch list?
In short, if you’re trying to prevent more gun deaths, a measure like this barely qualifies as “window dressing.” Better than nothing, but only by an amount so small as to be imperceptible. Closing the gun show loophole would be marginally better. But until we decide that military grade weapons don’t belong in the hands of anyone not in uniform, ban the sale and possession of them, buy back the ones that are out there, and feed them to the crusher, we’re just masturbating.