[Myrddin]

Once you have fired thousands of rounds...many reloaded from brass off the range floor...this is a totally useless exercise. It would only find the most naive individual firing brand new factory ammo from a completely clean firearm. Use of revolvers to retain the brass, gloves to prevent contact between skin and cartridges/firearm will completely defeat this approach. There is also the matter of discerning the difference between who loaded the gun and who fired the gun. Frankly, it's just another solution in search of a problem. A worthless technology (like microstamping) that will only gain traction if mandated by the government. There is no market demand for it.

[An Old Man]

"...this is a totally useless exercise."

It's difficult to argue with that. If I may offer another solution to the problem.

Perhaps, we could pass another law. We could simply request the criminal leave a note at the scene of the crime just like when you park to close to my new car and accidentally put another ding in the side of the door.

Simple, cost effective and except for the criminal should not offend anyone.