I have never seen any military manual listing hammer down on a loaded round as a standard condition and have never seen this practiced by any military user, it is more fumble prone than condition three. Poorly trained people are prone to do all sorts of odd things with weapons they don't understand and the 1911 is not immune to poor handling. Is it safe to carry a 1911 hammer down on a loaded round? Yes, for the most part, but what advantage would this offer over cocked and locked or condition three? The disadvantage is the slow time to readiness and danger of lowering the hammer on a live round and perhaps this is the reason for the larger spur. The practice was recognized as dangerous, but people did it anyway.
Back to the original question of the grip safety. It is apparent that the grip safety plays no role in a pistol carried cocked and locked, hammer down on a loaded round, or condition three. So when does it come into play?
Only in a cocked and unlocked pistol, and it serves to block the trigger when the user drops the weapon or lets it dangle from a lanyard as mentioned before. Speculation on what JMB, the Army board or ill informed users have done in the past doesn't change the function of the grip safety.
One other thing many forget is that the thumb safety blocks hammer movement to some degree in a 1911 even if the sear or hammer notch were to break.
Back to the original question of the grip safety. It is apparent that the grip safety plays no role in a pistol carried cocked and locked, hammer down on a loaded round, or condition three. So when does it come into play?
Only in a cocked and unlocked pistol, and it serves to block the trigger when the user drops the weapon or lets it dangle from a lanyard as mentioned before. Speculation on what JMB, the Army board or ill informed users have done in the past doesn't change the function of the grip safety.
One other thing many forget is that the thumb safety blocks hammer movement to some degree in a 1911 even if the sear or hammer notch were to break.