Generally speaking, when a manufacturer tells you not to do something, it's for a reason.
Will American Rifleman be buying you a new Glock 19 if you blow up your gun or pay your medical bills if you're injured?
Yes, you can run a certain number of lead bullets through a factory Glock barrel before it's leaded enough to cause a problem. Do you know what that magic number is? Do you really want to find out?
It's your hand and your handgun, but if it were mine I'd give more weight to what the manufacturer says about their product than a periodical.