Many new GLOCK owners get concerned when they see nasty looking dings in the metal on the inside of their slides. This is commonly known as slide peening. After a round is fired the frame flexes under recoil and the locking block moves upward with the flex and dings or peens the slide.
It happens with al GLOCKS but it is most prevalent in the 40 caliber pistols. Peening is normal and generally nothing to worry about. Unless the peen ridges are so pronounced that they impede barrel movement you have nothing to worry about. If they do impede barrel movement you can remove the peening with a file or stone.**
It is possible to prevent peening all together on new guns. Before it is fired remove the locking block and remove 1-2 mm off the top using a mill.**
The picture below
shows a normal amount of peening on a G22 slide. If you still have
questions about peening or anything else GLOCK, click here to email
**This should only be done by a qualified professional.