1. Hammer down on a live round allows the gun to discharge, without you pulling the trigger.
2. Hammer down makes it impossible to engage the safety.
2a. A gun, not on "safe" is considered "unsafe". Not just to you, but to all those around you. No one should ever be endangered by a CCW weapon, except the person at whom you are pointing it. If I found a friend, at my home, carrying a 1911, Condition 2, I would ask them to leave. If you are carrying a firearm, in an unsafe manner, around my children....
3. Hammer down, makes your SA-only pistol a very slow and dangerous device, to use for the first shot. While you are cocking the gun, the bad guy is firing. I can't imagine a reason, for allowing your adversary this advantage, that will leave the realm of "I just do."
Yeah, we know you do. The question is why? If you don't even know the answer to that question, stop.... doing..... it.
