Rather than resorting to such extreme measures as attacking the interior of the existing barrel with a file or nitric acid, simply replace the barrel with a new one (normally not prohibitively expensive), then put a few hundred rounds through the new barrel at the range so that it appears used when/if examined. Naturally this does not address the possibility of unique marks made on the primer by the firing pin, on the cartridge by the ejector, etc. AR #%#%#%#%#%#%#%#%#%#%#%#%#%#%#% "In the end, more than they wanted freedom, they wanted security. When the Athenians finally wanted not to give to society but for society to give to them, when the freedom they wished for was freedom from responsibility, then Athens ceased to be free." - Edward Gibbon ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Allen Robinson.........................sebago@earthlink.net PGP public key FE4A0A75 fingerprint 170FBC1F7609B76F 967F1CC8FCA7A41F