I would think just routine firing of any handgun would cause any original tool marks to wear down over time to the point where the marks made on the original case wouldn't even resemble the marks made after the 1000th or 5000th shell was ejected.
5 minutes with a stone or fine sandpaper on the ejector or extractor would definitely make the original sample useless and what about those handguns that have replaceable parts?
I would think these facts alone would be easy enough to prove in court that any arrest or search warrant that was issued based on the original marking to be declare invalid and any evidence gathered from those warrants to be excluded.
This demonstrates the total lack of knowledge and intelligence of the liberal mindset. They craft legislation that is geared towards a steady state and don't consider that things can change. In this case, collect physical samples of a guns markings when new but those marking will change with use or maintenance of the gun, but the same applies to other issues. Need more tax revenue? Raise the tax rates. Of course, that doesn't consider that some people may change their income mix to avoid those additional taxes, or they may just move out of a high tax state.
I think the fact that $43 million has been wasted on this boondoggle without a single prosecution is evidence enough that this is a worthless policy and should be abolished.