>The probability of finding the pistol in this manner is not very good.<
Now they guy freaks out and knows he has to dump the gun or at least change barrels. They should have kept it quiet IMO.
Exactly. The barrel will be removed and destroyed. A replacement will be purchased with cash from some supplier...preferably one that keeps no records.
One can only hope the criminal is an illiterate who never gets wind of the investigation.
Sounds like they are looking for TWO guns here. A smaller caliber revolver is commonly carried as a "backup gun". Screening the LEOs .40 cal Glocks and backup guns sounds like a very reasonable angle. I wonder what the smaller caliber bullets yielded in terms of the rifling (twist, twist direction, number of grooves/landings). That is usually pretty manufacturer specific too...and MUCH harder to ditch compared to the typical barrel on a Glock.