I bought the first Glock .40 the local gunshop sold and started shooting IPSC with it. That first G22 went about 23K rounds before it failed. The reason it failed, and documented by myself through exhaustive metallurgical testing, and concurred with by Glock, was due to overpressure caused by lead bullets. Funny thing is that, as I write this, sitting right here at my desk, is a page full of numbers, numbers that luckily I recorded prior to the failure. I was shooting over a Chronograph when the gun blew and had over 120 rounds individually recorded. Each round had been measured and each powder charge individually weighed. I know EXACTLY what the loads, powder charges and velocities were. I look at the numbers now and wonder how I did not pick up what was occurring. But hey, I was young. This was almost 10 years ago.
As I write this, I have a G22 with over 80,000 rounds through it, a G35 with over 15,000 rounds through it, a G27 with over 20,000 rounds through it and I sold a G24 with 15,000 rounds on it, a G23 with 6,000 rounds and a G35 with 2,000 rounds on it (does not count since a KKM barrel) So I have fired 159,000 rounds of .40 through Glock factory barrels.
I have pressure tested lead bullets fired in actual Glock barrels with controlled test conditions and the same loads fired in conventionally rifled barrels. Then I fired jacketed and copper plated bullets in the same conditions to test for pressure increases there. Conclusion is that lead bullets, yes, even the 24 BHN variety, increase pressure after only a few rounds fired. When the pressure reaches an unsafe level has to do with the powders pressure curve, temperature, bullet hardness, bullet grain structure. Weak cases do let go, but do not result in the same type of damage.
When a Glock is overpressured, the shooter is rarely injured beyond a few cuts or bruises on the shooitng hand, none that I have seen have been permanent. And how many have I seen? To date I have personally inspected over 40 blown Glocks that were the result of overpressure. I have reviewed documentation on over 120 others. And, yes ALL calibers were represented.
And how would I know what I am doing, besides just being a shooter? I am a forensic engineer (mechanical) who investigates accidents and failures for a living. I have been qualified in court, as an expert (which is not easy these days). And for the record, the firm I work for does more defense work than plaintiff work. We work for who hires us and, sometimes, our clients do not like our findings, but that is the breaks, facts are facts, evidence is evidence.
Glocks are not perfect, nothing man-made is, but I trust my life to their reliability. I reload (couldn't afford to shoot if I did not). For me, I choose to shoot plated bullets which cost me a few dollars a thousand more than lead. I save on the cleaning stuff and the cost is about the same as lead. I also use the factory barrels, exclusively now (I sold my KKM barreled G35).
The overwhelming majority of blown Glocks are from lead or poor quality reloads. A few are from bad factory loads and a few from defective aftermarket parts. I must beleive that there are a scant few that have had manufacturing defects, but I have not seen one yet that casued a KB. If I do, Glock will surely be hearing from me, and I believe they will do the right thing.
Hope this helped.