Your instincts are correct - there's nothing wrong with FMJ ammo, and in fact, probably 95% of popular practice and defense handgun ammo is FMJ.Nikolay_Yordanov said:i am not really sure if that guy knew what he was talking about
Perhaps he was referring to TMJ (total metal jacket) ammo, but I still think that such ammo will have no negative effects on the gun.
Just FYI - Glock pistols do not recommend using anything other than jacketed ammo. Un-jacketed bullets are pure lead, and the lead will foul the rifling of Glock barrels (though some say slower rounds are ok).
So in conclusion - get your "friend" some education. He's clueless.