It is only lead bullets that can cause problems. Jacketed bullets should be fine...barring an overcharge. The polygonal rifling in the stock barrels apparently are subject to more leading than conventionally rifled ones. If the glock barrels are not cleaned properly it can cause a potentially dangerous rise in pressure than can cause a Kaboom.
There are lots of threads on this all over the internet if you care to google it somemore. Here's a link to a glock faq that explains it better than I can. Also be aware that use of reloads can void the glock warranty.
The Glock FAQ: glock_faq_reloading