imported post
Taking the barrel (preferably NOT still in the gun!!!!!!:shock
and looking through it at a bright light should show....
Well defined rifling with no scratches.
Rifling that goes all the way to edge of the chamber. If the rifling seems to get less defined close to the chamber the barrel is becoming "burned out" from the blast of fire when the powder is ignited.
Look at the muzzle... there should be no nicks, scratches, or damage of any kind.
Look at the barrel itself from the outside... there should be no bulging along the length. Lay a straight edge along the length of the barrel if there is any question in your mind.
Glocks use Polygonal rifling (please do a 'net search for Polygonal Rifling for more info on that) that has more like hills and valleys so the rifling won't look the same as others that use conventional sharp edged looking "lands and grooves".
The good thing about pistol gun barrels is.... they last a very long time. Generally the barrel will outlast the owner of the gun.