I'm on my second Gen 4 Glock 20 - I sold the first one and then bought a replacement when I moved from Texas back to Canada. Both of them have eaten everything I've fed them without a hiccup. To be fair that's just been LAX hardball for practice ammo and the Underwood 180 grain 1300 FPS load.
I've spent a lot of time and money on modern semi-auto pistols, and what I'll tell you is that the Glock is the Toyota of the firearms world. Bland, devoid of personality, not as high performing as some other firearms....but they have a cult following because they just plain work, even if you aren't very nice to them.
Based on my experience I would be hesitant to put a bunch of cast lead rounds (more than 100) through a Glock factory barrel. Coincidentally, 100 rounds is the number that my personal fuss-ass-ness tells me that I want to run through a pistol before I decide that a particular combination of round and pistol meets my requirements for "serious social purposes". Oddly enough, every single Glock I have ever owned has digested every single factory load I have ever fed it for all of those 100 rounds without even a hiccup or burp. Just like Toyotas, Glocks are boring and reliable.
If you're really worried about it, slap an inexpensive (used?) aftermarket barrel with conventional rifling into your G20, shoot the 100 rounds of your desired bear load through it to verify function, and call 'er good.
I've spent a lot of time and money on modern semi-auto pistols, and what I'll tell you is that the Glock is the Toyota of the firearms world. Bland, devoid of personality, not as high performing as some other firearms....but they have a cult following because they just plain work, even if you aren't very nice to them.
Based on my experience I would be hesitant to put a bunch of cast lead rounds (more than 100) through a Glock factory barrel. Coincidentally, 100 rounds is the number that my personal fuss-ass-ness tells me that I want to run through a pistol before I decide that a particular combination of round and pistol meets my requirements for "serious social purposes". Oddly enough, every single Glock I have ever owned has digested every single factory load I have ever fed it for all of those 100 rounds without even a hiccup or burp. Just like Toyotas, Glocks are boring and reliable.
If you're really worried about it, slap an inexpensive (used?) aftermarket barrel with conventional rifling into your G20, shoot the 100 rounds of your desired bear load through it to verify function, and call 'er good.