The Z5 has the recoil lug and action attached to the barrel with screws. The other is welded. The Z5 firing pin removes from the rear of the breech block. The regular omega had a blued steel triggerguard and the z5 has a powdercoated alloy guard. That was the only thing I didn't like about the z5. Absolutely superb rifle. Its replacements don't hold a candle to either version imho.