I shot thousands of lead boolits through my G21 when I had it. The G21 would be the safest glock to do this with because the 45acp operates at such low pressure that you actually have a pretty good leeway with the pressure curve, since the same size design will handle the 10mm just fine.
Besides, if you use a .452 at <1000 fps, it seals well and doesn't lead appreciably. When it does if you shoot it that much, it's very easy to clean out as noted. Keep it clean, if you do shoot jacketed bullets through it at the range, shoot them first, before the lead.
I would be a lot more careful with other caliber glocks and lead. 9mms operate at ~35K IIRC? Not much leeway there! Be careful, use your head and you'll be fine. Don't shoot jacketed after the lead because if it's leaded, there's where you'll get your pressure spike. That crap that is repeated about shoot jacketed to clean out the lead is stupid and a wives tale.
I couldn't get the lead SWC's to feed in my G21 but it loves RN.