Oooh, I've been linked!

Smallest Minority did it in a post with LOTS of details on ballistic fingerprinting. He's got lots of links including to the California and Maryland studies/programs. And lots of excerpts from the experts saying "this stuff ain't DNA". Including,
"The AB1717 Evaluation was designed to test the performance of the IBIS™ system for the anticipated large database of new firearms. The experiment used 792 Smith & Wesson model 4006 semi-automatic pistols for this purpose. Each pistol was test fired using at least two cartridges of Federal brand ammunition and other ammunition. One of the test fired Federal cartridge cases for each of the pistols was registered into the database.

The duplicate Federal cartridge cases from fifty of these pistols were selected at random and compared with the database. The system ranks how well each entered mark matches the evidence. The higher the ranking the more similar the stored image is to the evidence’s mark. For the system to be successful, the correct gun should be listed in the top few ranks. The results show that 38 % of the fifty pistols were not listed in the top 15 ranks. The same experiments was repeated with ammunition of a different brands. In this case 62.5 % of the pistols were missed and not listed in the top 15 ranks. These results will be discussed in light of the investment in terms of equipment and personnel needed to set up a ballistic fingerprinting database. In fact, the trends in the obtained results show that the situation worsens as the number of firearms in the database is increased."

Ok, these test guns were fired with the same brand and type of ammo from the same manufacturing lot and they still got such lousy results!

Go over there and read the whole thing, he covers it very well.