[glock30]

I don't think that is a crack on the chamber. I looked at it magnified, look at it close with a magnifying glass or with the naked eye and tell me what it is, just looks like a mark or deep scratch, these things don't crack too easily, unless someone changed or did something with the barrel and exerted too much violence....You really got this at a good price, I wish I could find one for that. Take another picture of the chamber if you would , closer to the chamber than the one as you posted.