I've shot plenty of lead through Glocks without any issue...a couple hundred rounds without cleaning. The only reason you can't shoot lead through a glock is due to accumulation of lead from not cleaning but that would take a lot of of shooting. Back when I managed a gun shop/range we put thousands of lead rounds through the glocks without incident.
BTW, you can't shoot reloads through many firearms either....they'll blow up the gun. That's why shooting reloads through most guns voids the warranty. Check your paperwork, it probably says to only use factory ammunition.