Glock pistols use polygonal rifling, and therefore it is not recommended to use straight lead rounds. Due to excess fouling caused by straight lead, resulting in increased pressures in the barrel, one must shoot at least a semi-jacketed bullet through all polygonal rifled barrels. This includes Glocks, select H&K pistols such as the USP and the P2000, and the Baby Eagle/Jericho series.
As previously noted, however, Glock, like all other manufacturers, will consider their warranty void if reloaded ammunition is used in their products.