If you go to the link above for "safety" and scroll down the page. The bolt on the left is a later production Universal. With no protruding bottom "tail", the carbine hammer can hit the firing pin out of battery. VERY hazardous. If your bolt has a tail on the firing pin like the one on the right, there is less chance of out of battery discharge, provided the receiver has the bridge with the safety notch. I have seen Universals with a GI style bolt and no safety bridge, too. Those can discharge out if battery, also.