Bulged brass really isn't a problem, except that it shortens brass life. The cost of an aftermarket barrel buys a LOT of brass. I found a Gen 3 barrel to smile, which ruins the brass with a sharp line, right around or above max book loads, which would have been right around max pressure. Doesn't seem to be a problem if you don't mind sticking to safe reloading practices, and you get the benefit of the excellent reliability Glocks are known for. This makes sense, the manufacturer needs enough case support for spec loads, but beyond that the larger chamber helps reliability, so why tighten it up?
I did end up buying an aftermarket barrel for added length and to run a compensator, and was squeamish when I realized that I could run the pressure higher without the same signs. If you get a kB in a stock barrel, it smacks your hand, dumps the mag, and cracks the frame. What happens when the case support allows pressure to build much higher before releasing? Then what is the failure point? Does the chamber peel apart and blow bits of slide into your eye?
As it sits, my reloads will smile a bit in the factory barrel, but not in the AM barrel. If I get them mixed up, it won't mess the gun up if they go through the stock barrel, but it will ruin the brass. I am pretty sure they are over spec, but not by a huge amount. For the risk and the added 1/2" of barrel, I get about 90fps. Whether or not that would be worth it is up to each person. -Edit- You could probably equal the performance with a safer system overall by going to a 6" barrel, whether it was Glock or AM.
Last edited by Any Cal.; 01-03-2013 at 00:34..