An easier alternative would be to just file off a few thou from the end of the firing pin or what not, causing the stamping to be all but gone.
But I forgot, the criminals are surely going to abide by the law, and turn in their illegally purchased\stolen firearms to be converted for microstamping. The over 2 million illegal handguns reported to be in NYC alone by the NYPD will be turned in for conversion, not a doubt in my mind. It'll work as well as COBIS did, because as we all know the law abiding citizens are the ones shooting up the streets.