And they work. If you drop a decocked 1911, PPK or Beretta 92S on the hammer the gun will not fire - despite not having automatic firing pin blocks. However, in testing and reality, most 1911s with steel firing pins will fire if dropped muzzle down on a hard surface. This isn't a super dangerous situation as the bullet is going into the ground, but still not awesome. But an inertial pin hitting a primer hard enough to fire requires that it gets up to speed. When the hammer is down, the firing pin is placed much closer to the primer, and has less room to accelerate (relative to the primer) when dropped. So would a 1911 that would fail a CA drop test with the hammer cocked, pass if the hammer was down? (Or any other pistol with the same firing pin configuration.) It seems like it would be less likely since most guns end up with the FP barely 1mm off the primer when the hammer is against them.