O-Frame Cocked and Locked

[inboost]

I think it's important to note here that the magnetic field was most likely only responsible for rapidly moving the gun from the owner to the machine. The firing pin went along for the ride and didn't move with respect to the slide while the gun was airborne. The gun coming to a complete and very rapid stop upon impacting the machine wasn't even the problem. What gave us the discharge was the inertia of the firing pin it's self.

Just like in an automobile accident there were multiple impacts. During a simple straight-on collision with a wall the car stops first, then your body hits the seat-belt/steering wheel/etc. and finally your internal organs hit your skeletal structure.

The gun stopped, but the suspended and mysteriously 'unlocked' firing pin continued it's travels until something interrupted it's flight. The spring was first, but it seems the primer was also responsible for stopping the firing pin and thus we had the ND.

Here are three scenarios, all the same, which would fire a chambered round from a 'series 70' O-frame 1911 gun which has no such firing pin safety:

1. Hammer released from cocked position in normal firing of the gun
2. Gun dropped from a moderate height muzzle first on to a hard surface (cocked or not, safeties engaged or not)
3. Gun rapidly yanked from rest in a direction opposite the muzzle (cocked or not, safeties engaged or not)

#1 The hammer imparts a velocity to the firing pin when it smacks it. This transfer of energy takes the firing pin from rest to a high rate of speed in the chamber direction. The firing pin spring tries to resist this motion, but the engineering staff dutifully picked a spring rate that would not interfere with the purpose of pulling the trigger, to fire the round. Therefore the spring only slows the firing pin enough to keep it from puncturing the primer or becoming wedged in the breech face firing pin bore hole. The pin hits the primer and the final few Joules of energy are exhausted when the primer is deformed enough to begin releasing it's chemically stored energy. Now that forward motion of the firing pin has come to a stop the firing pin spring (which transfered kinetic energy into stored spring energy) is free to go back to it's restful, less compressed state such that it moves the firing pin back to it's home position in the slide. The gun awaits your command to fire again!

#2: The gun in it's entirety is in motion. All of it's parts develop kinetic energy . Kinetic energy is directly related to mass and the square of speed. So the faster the parts are moving and the heavier they are, the more energy they store with speed having a much larger effect than mass. As stated above, when the gun hits a hard surface it stops moving. It's kinetic energy is dispersed quickly into what it hits. The nose of the gun deforms where the metal is pushed past it's yield strength, or springs back were the metal isn't pushed past it's bending point. The firing pin slows down as it works against the spring force exerted by the firing pin spring which is trying to keep the firing pin away from the primer. The spring force is a simple constant multiplied the amount the spring is compressed. The more you compress it the more it pushes back. If the inertia in the firing pin is low enough, the spring will 'absorb' the firing pins energy and bring it to a stop in it's forward travel before it taps the primer. If not the firing moves just as if it had been hit by the hammer and discharges the round. Hence the series 80 firing pin block. It interferes with forward travel such that instead of relying on a spring to absorb the transfer of energy, the firing pin block takes the impact and disperses it into the slide.

#3 is identical to #2 except in this case the frame of reference has been reversed. The firing pin has yet to begin to move (body at rest remains that way until acted upon by an outside force) while the gun has already begun to zoom off in a direction opposite to the muzzle. The mechanics of this situation are that the moving primer slams into the stationary firing pin. An analogy would be dropping a bullet primer first on to a firing pin anchored in a vise. The newer gun with the series 80 parts would again not go off. The series 80 firing pin stop would bring the firing pin up to speed of the gun as it would impact the stationary firing pin long before the primer could. It would be difficult to make this happen because we need the gun to change it's velocity very rapidly and because it's a lot heavier than the firing pin this is much harder to do.

The most important thing learned here? The gun in the MRI case would have fired even if it had not been in the cocked-and-locked state! Furthermore, if the hammer had been down the chances would have increased for the ND because the firing pin would be slightly closer to the primer (hammer pushes it in when at rest against the firing pin stop plate). It would have also increased the chances of the ND if the gun had it hammer first as it would have transferred energy into the firing pin just like a set of billiard balls hit from one end knock the one on the other end away from the group.

Moral of these stories: Cocked and locked = safe!

[WKC]

I think Inboost covered the possibilities. One thing to keep in mind with the experiment with the magnet is that the magnetic field from a small hand magnet is very localized. It will suck the firing pin in relative to the slide. That's because the slide is being held in a stationary position in the experiment. However, in the incident, the magnetic field is much larger, affecting the whole gun and not just the slide or the firing pin. So, the whole gun is being accelerated towards the MRI machine by the magnet, not just firing pin.

I think the most plausible explanation for the AD is that both the firing pin safety and the firing pin moved as a result of the impact against the MRI machine. Throw a little Murphy in there to make it happen in the right sequence and you have an AD.

As for why the gun is referred to as the O-Frame, I'll wait until our High Priest of Gun Sluts and all things that go bang, (CCWI), to explain that one.

[Hoser]

Originally Posted by X-ffdo

Murphy was there!

Roger that, ffdo!

[CCWInstructor]

It is possible, yes. Can it happen, who knows.