I've fired lead in a Glock, including a nice accurate load with 180-gr cast bullets (only BHN--8? it was 13 on the SAECO or whoever's lead hardness gizmo) wtih WW231 that made smiley-face marks on the brass. Quit that FAST before the kB!s were commonly known.
Anyway, I think the lube is more important that hardness. I've tried both Laser-Cast and Rim Rock hard-cast bullets, BHN above 20, and they actually leaded a bit more than those 180s I cast myself. Accuracy has always been disappointing.
But WORST is that it takes forever to get the leading out!!!:banghead: They all lead very very little, about 1/4 what I get with revolvers, but even a stainless steel brush makes slow work of it. It's just as hard to de-lead as a revolver. Less leading but equal work?
I inspect the bore regularly and never fire more than about 100 rounds of lead before a cleaning anyway. Back in '95 or so, I asked a friend who worked then at the Gunsite Smithy if he had ever seen a Glock let go. Only one, it was only a case failure (not a "true" kB! according to the term's originator, formerly-famous gunwriter Dean Speir), and it came after about 800 rounds of lead loads, without cleaning.
I've read all those pages on Glocks and lead years ago, and have concluded that it's largely alarmist over-reaction with a solid basis in truth. Load light, pay attention, don't double-charge and keep the round count DOWN and I believe you will be okay.
And don't try to get more than 925 fps out of a 180-gr LRN using WW-231 in a 4-inch barrel. You need slower powder for higher speeds with that bullet weight.