As an ammunition manufacturer, we load a lot. We also have a vested interest in making sure our ammunition will function correctly in as many firearms as possible. One of our staples in handgun loading is the .40 Smith and Wesson. In reloading circles, there is a lot of myths around the brass from this cartridge, particularly the brass shot from a GLOCK. This is an attempt to dispel some of these myths.
We load on Dillon 1050s and use Dillon dies. These dies are set up according the Dillon's instructions. We use no other extraordinary means in our loading process. Before we set our ammunition out for sale, a second person performs a quality assurance check on every individual piece of ammunition. For ammunition for an semi-automatic handgun (9mm, 40 S&W, and .45ACP) this includes case gauging every loaded round. If the round does not fit properly in the case gauge, it is set aside, and later roll-sized. The brass we use has been shot out of who knows what, who knows how many times.
Since we case gauging every loaded round, I can give you an exact number of cartridges that have a bulge at the bottom of the case, or the infamous "GLOCK bulge." Out of our last run of .40 Smith and Wesson that I did, I loaded 3,000 rounds. 18 rounds did not case gauge. This is a less than 1% failure rate.
In the interest of data gathering, I took these and loaded a magazine for two different pistols before we roll-sized the rounds - a GLOCK 23, and a Kahr K40. I hand-cycled each round through the action, and they all went into battery just fine.
By comparison, when I last loaded 9mm, I did 3,000 rounds. Like the .40, the brass is from a variety of sources, and we have no idea how many times it has been shot, or what it has been shot through. By the time it makes it to the reloading machine, even the tell-tale H&K fluting marks have gone. Again, we use Dillon dies on the Dillon 1050, and case gauge each round. The above-mentioned batch had 23 that did not case gauge, still less than 1%, but slightly more than the .40 Smith and Wesson.
What does all of this mean? Simply put, .40 Smith and Wesson brass should not give you any issues, even if it has been shot from a GLOCK. If you set your dies up according the the manufacturer's instructions, there shouldn't even be enough of an issue to notice.
