Franzen Security: Franzen Interbore Bore Lock B-31

Does its job legally, but I cannot help feeling that it is deforming the headspace of the chamber and scratching the barrel.

Be VERY careful with these locks. In some states such as Maryland these are excellent locks for complying with state requirements of a bore lock when purchasing a handgun.HOWEVER Cheap does not mean good. These locks work by shoving a metal rod into the bore of the gun with a small plastic end that goes into the breech chambering area. The plastic end serves as a "protective cap" to prevent the metal from ruining the delicate rifling inside of your handgun. But, the metal used in the lock is not stated as softer than metals used in gun bores. There's a good chance that if you end up touching the walls of the gun bore with the lock metal you'll end up scratching up the inside and thus the rifling.Also this thing is nowhere near secure. With an old gun I was able to pull it out easily even when locked. The reason is that the locks are simply to ends of metal on a rod that expand a bit when locked. If you pull out hard enough the metal will bend back and at the same time destroy the rifling ridges in the bore of the gun.