There are 2 kinds of shooters on this thread,... those that have blown up Glocks, and those that will blow up Glocks! Personally, I have blown up a G34 with an aftermarket barrel and plated bullets (a Federal case, by the way).
The lead thing? I have a G21 with about 80,000 lead rounds thru it. The first 5,000 or so with the factory barrel, until I noticed the BULGE. WHOA, went to a Bar-Sto immediately.
Using lead bullets deposits lead at a much greater rate than copper, either plated or jacketed. So, the same number of lead rounds will reduce the 'effective bore diameter' at a faster rate than copper. Ok, well, so pressure is not a first order response to bore diameter reduction. In other words, a slight diameter reduction could lead to a 5 to 10 times pressure increase, and therefore, KB!
Of course Glock would say any non new factory ammo could void the warranty. And they are positively correct about American Ammo!!!