By factory barrel, I assume you are referring to Glock.
I have loaded and shot thousands of rounds through my stock barrel (Gen 3 G20) and have never had a failure. I practice good loading practices and don't shoot max pressure loads more than once - and only in new brass. Some folks will shoot two to three rounds at hot pressures, but I tend to be pretty conservative.
I full length resize and relegate spent brass from full-house loads to the practice assortment. In my practice assortment I have only found one split, and that was a nickel-plated Remington that split when re-sizing. Other than that one exception, cases have been retired because they eventually shrink below minimum specs. That seems to be the limit on case life for me. My practice/IDPA loads are 180 gr @ 1050 fps (about like a near max .40). I carefully inspect and measure each case after re-sizing. I have had fine results.
In some situations with the Glock barrels, the infamous "Glock Smile" rears its ugly head. I would not re-use any brass exhibiting such signs. A smile indicates that there is a pretty sizable stretching (and weakening I imagine). A bit of a hog belly bulge is normal for a Glock barrel. I only recently encountered smilies in my own gun. I had previously shot plenty of hot stuff and never seen one. They cropped up when using 800X powder and 180gr + projectiles. I don't load 800X and heavy projectiles for this reason. A9, A7, and Blue Dot have worked great. 800X is awesome behind 135 grainers though. Also the loads from our favority 10mm ammo manufacturers have been fine too.
In my experience, use good handloading practices and only load the hot stuff in new brass. I have had great results.
Last edited by Taterhead; 01-21-2010 at 23:57..