Correcting a couple of mis statements in prior posts. Because for some reason some folks seem to think the 40 caliber uses "high" pressures and older calibers don't.
Per SAAMI. The maximum operating pressure for the 45 ACP is 21,000 PSI. The maximum operating pressure for the 9mm Parabellum is 35,001 PSI. The maximum operating pressure for the 40 S&W is 35,000 PSI. The maximum operating pressure for the 10mm is 37,500 PSI. The maximum operating pressure for the 357 Magnum is 35,000 psi. The maximum operating pressure for the 357 SIG is 40,000 PSI.
Conclusions. First, among the most popular semi auto calibers the only one that operates at a "low" pressure is the 45 ACP. The 357 Magnum wasn't the first high pressure pistol caliber as some believe, the first pistol caliber in wide use that operated at a "high" pressure was the 9mm Parabellum at 35,001 PSI and that was derived from the 7.65 Parabellum at 34,000 PSI. IMO the 357 Magnum likely was in part a result of the 9mm Parabellum demonstrating that brass pistol cases could safely withstand these operating pressures. It's also worth noting that the 9mm, the 40 caliber, and the 357 Magnum all operate at the same maximum pressure and it's not that "high". If you want "high" pressures today you can start with the 10mm @ 37,500, move up to the 357 SIG @ 40,000, and then go on from there to the 500 Magnum which features a maximum pressure of 60,000 psi.
Now, what happens when you "Glock" your brass. First, you get a bulge in the area of the feed ramp intrusion into the chamber. Since this bulge won't permit a reloaded round to chamber that bulge has to be sized back down, what is typically called "bulge busting". Every time you do this you work harden that area of the case and sooner or later that work hardening can produce unseen micro cracks in the wall of the case. Folks, Cracks aren't very strong, in fact a Full Depth Crack has no strength whatsoever under tension. Fire a case that has been badly compromised by microcracks and if that area isn't well supported it will blow out. If it's bad enough, even a well supported case will have a case head seperation.
BTW, Feed Ramp Blowouts are fairly benign, they usually just destroy the frame on a polymer pistol or blow the grip panels off a 1911 and badly bruise the shooter. Triple charges of a fast powder such as Titegroup can cause Death, so anyone who reloads needs to take steps to insure they won't ever produce a double or triple charge. I would also suggest taking steps to reduce the chance of a feed ramp blowout because by every report I've seen they really do sting and you usually total your pistol.
BTW, a simple test for case support is to pull the barrel, chamber a case or round, and look at the the case exposure in the area of the feed ramp. If you can see any casing above the edge of the extractor groove chamfer you may have some partial support. Because with a semi auto the "floor" of the case head commonly stops at the edge of that chamfer or at most 1/16 inch above that edge. How much lack of support exists is determined by how much of the side wall of the casing is exposed. Note, the radius between the chamber and feed ramp doesn't provide any support so you need to include that in your evaluation. If you want to get really exacting you could use Prussian Blue paste to butter the chamber wall and then insert and remove a clean case to determine the "fingerprint" of the support. BTW, use a long wood dowel down the barrel to "roll" the case a bit for this and to poke the case free. Note, Prussian Blue paste can be found at NAPA and Repair Shop level Auto Parts stores because it's perfect for checking the seal of a freshly lapped Valve Seat on a cylinder head.
