Pretending what others believe to be a problem doesn't exist (despite you admitting that it does exist, just not significantly) doesn't solve anything.
So this means you'll be voicing your support of voter ID any time now, right? I mean, it fits every criteria you just laid out.
The bottom line is that gun crime is a symptom of a larger problem: systemic poverty and the degradation of morals.
A gun, at its most basic, is a force equalization tool. You dont have to be strong to defend yourself with a gun. If she's a good shot, granny could take down Arnold Schwarzenegger.
Trying to solve "gun crime" preconceives your solution based on the problem you stated and will just drive criminals to other weapons as it did in England.
But let's look at this specific idea, micro stamping casings. There is no way it would stand up by itself in court, as was pointed out all you need is to collect and plant a casing.
It would make far more sense to magnetically encode something into the slug, but again technology that doesn't exist but at least there you are tying the identifying information with the correct piece, the one that kills or maims.
How do you intend to differentiate casings from real bullets vs blanks? The casing is identical.