The warning that you shouldn't shoot reloaded ammo is largely a lawyer thing, as far as I know.
I've never actually shot any measurable amount of factory ammo out of my Glock (Gen 3, 26) and have never had problems. I guess my question is this:
Are you worried about it because you read about Glocks kabooming because of unsupported chambers?
- Don't worry about it. If it's a quality reload, which it had better be coming from a factory, you'll be fine. Just don't shoot too many lead rounds through any polygonal barrel in a row. They don't like it.
Are you worried because it looks shadily made?
- I don't shoot shady ammo, whether it's brandspankin' new from the factory, fond on the ground in the mud or self made.
Just don't buy too much into the internet myths regarding any guns, really. According to the internet, a loose 1911 never happened, a .38 never killed anyone, Taurus are hand grenades and not guns, every Colt from before some random date works forever under any circumstance, pistol grip shotguns lose all capacity for any use whatsoever .... the list goes on.