Having right around 4000 rds through my Sig M400, of primarily steel cased ammo, it got me thinking about my barrel after reading this. Just using a bore light I can't see any obvious wear or damage in the bore or chamber. I don't think I'll be slicing it open for further inspection! Same with the extractor, just no noticeable wear. Now I have never shot it to the point of being blistering hot, nor have I gone an extreme high number of rds before a bit of cleaning. Accuracy is still very good, though I have not bench rest shot for some time. Just makes me start thinking twice about bi-metal bullets.