What could cause the breech face of my glock to have little chunks taken out of it from the top of the firing pin hole all the way to the top of the slide. Its like someone took a chisel and hit it a couple of times there. Could this be from an aftermarket barrel that wasnt fitted correctly? I checked to see if my barrel was causing this, and it appears to me that my barrel is not rubbing where teh groove is. I posted over at Glock Talk but didnt get much as far as answers. The groove is maybe 1/32 of a inch deep and runs all the way to the top of the slide. It is visible from the top of the slide. Maybe this is common with some Glocks, but I have owned 5 before and never seen this before. Gun supposedly has about 750 rounds thru it, and that sounds about right from looking at it. Is this a problem?