Inertial firing pins - less drop safe hammer cocked?

[Vern Humphrey]

Vern, I don't know how you are able to separate the velocity of the gun from the question of dropping a gun.

I'm not sure I understand you.

The original question is, “Inertial firing pins - less drop safe hammer cocked?”

Under the conditions of that question, we have two identical guns, one with the hammer cocked and one with the hammer down. The only difference is that one has about 0.1” of firing pin drop more than the other.

It’s easy to calculate the added velocity and kinetic energy of that 0.1” drop. And that is the ONLY difference between the two pistols. Those calculations show that tiny amount of added kinetic energy is not enough to cause the pistol to fire – by itself.

 

[RX-79G]

Lets suppose there is a theoretical drop safe advantage for a 1911 with the hammer down vs a 1911 with the hammer cocked. I don't know there is, lets just say there is for the sake of argument. I believe any safety advantage you'd gain in the rather unlikely situation of dropping your gun directly on the muzzle from a specific height where a discharge could occur, is outweighed by potential for an accidental discharge of lowering the hammer to put the 1911 into Condition 2.

1911s are just one of the guns we're talking about - but it is the one we're most familiar with. What I'm getting at is that 1911s, because they are carried cocked, have given inertial firing pins a bad name for drop safety. I think that inertial firing pins are for guns carried hammer down, and when carried hammer down are much safer than cocked 1911 drop tests make them appear.

Ideally, modern 1911s would be safer for cocked and locked carry with full length firing pins.


Vern,

You are talking about the difference in a vacuum, ignoring what else is going on in the story.

I'm talking about a firing pin colliding with a primer and their relative velocities to each other, but you just want to talk about the firing pin only.


If you drive your car into a parked truck at 5mph, nothing should happen because of your bumper. But if you drive your car into an oncoming truck, the result will be different even if you are still only going 5mph. Now the truck's velocity is a factor in the collision speed.


The increased space between the two firing pin start points allows the gun to be at different velocities when it collides with the firing pin, because the additional space allows the gun to rebound more than a small space. Or in the case of a Makarov - no space.

 

[Vern Humphrey]

Vern,

You are talking about the difference in a vacuum, ignoring what else is going on in the story.

I'm talking about a firing pin colliding with a primer and their relative velocities to each other, but you just want to talk about the firing pin only.

Okay. Explain how the rebounding pistol could have MORE energy because the gun was cocked.

The ONLY difference between our two theoretical pistols is one is cocked, the other is not.

 

[JTQ]

RX-79G wrote,
What I'm getting at is that 1911s, because they are carried cocked, have given inertial firing pins a bad name for drop safety. I think that inertial firing pins are for guns carried hammer down, and when carried hammer down are much safer than cocked 1911 drop tests make them appear.

Is there a big world of guns with an inertial firing pin and no firing pin safety.

 

[Walt Sherrill]

Like a head on collision, the downward moving 10m/s pin is going to strike the 4m/s upward moving gun and primer. 10+4=14m/s, which is 1m/s more than needed to pop the primer.

Head on collision? As I've said more than once, my understanding of physics is limited but growing. I know, however that two cars traveling at 50 mph that hit head on show the same damage as one car hitting a solid bridge abutment. It may be, as you claim, the kinetic force of the firing pin is not sufficient to depress the firing pin spring to strike the primer. That remains unclear, to me.

The barrel and slide hitting the concrete floor (as is done in the drop tests) makes the barrel and slide, at least temporarily, a wall for the firing pin. If there's not enough kinetic force between the spring and firing pin spring at that instant, to have the firing pin strike the primer, I don't understand why there is suddenly more force available after the barrel bounces, for that to happen.

It's the same firing pin spring -- but it's now pressing against the firing pin rather than being pressed by the firing pin.

It seems as though the firing pin, since it didn't have sufficient force to depress the firing pin spring enough to bridge the gap, may have stopped, and ought to (after the bounce) be doing what the firing pin spring is doing: starting to move in the other direction along with the barrel and slide.

In other words, I don't understand why the firing pin continues in it's original direction after the bounce, when it has seemingly stopped and everything else is now moving in the opposite direction.

Maybe it doesn't continue to move forward but tries to stay where it stopped and in doing so, finds the primer moving closer. it hasn't done anything that it didn't do earlier, and the spring is just as strong as it was when it first dropped (maybe stronger, since it has been compressed).

(I went to a small country school, and never had a chance to take physics -- didn't need it in college -- and I'm not trained as an engineer, so some of this seems almost magical, to me.)

What I'm getting at is that 1911s, because they are carried cocked, have given inertial firing pins a bad name for drop safety.

The guns tested in California -- including 1911s --are NOT tested with the hammer cocked (or cocked and locked). Some still don't pass.

 

[RX-79G]

Okay. Explain how the rebounding pistol could have MORE energy because the gun was cocked.

The ONLY difference between our two theoretical pistols is one is cocked, the other is not.

They don't have different amounts of energy. They have different amounts of kinetic energy on different vectors. Would you rather hit a car going the same direction as you, or in the oncoming lane? Does a car coming at you have more energy than a car driving next to you?

Is there a big world of guns with an inertial firing pin and no firing pin safety.

Yes. Every pistol made before 1978 (or so), and quite a few after. The new Baby Eagle I bought in 1994 didn't have a firing pin safety.

That would be okay if guns had expiration dates, but there's 100 years of inertial firing pin guns out there.




Walt,

The gun and firing pin initially are going the same direction. Then the firing pin is moving and the gun is stopped. Then the gun is moving up and the firing pin may still be moving down.


Hitting a buttress is like hitting a car of the same mass head on at the same speed, but it is also like hitting a truck of twice the mass at half the speed. The gun has 100 times the mass of the pin. But that's only important if you want to know about what happens to the two things that impacted, but we are really only interested in what happens to the primer, and all we really need to know is what how fast the pin was moving relative to the primer.

The guns tested in California -- including 1911s --are NOT tested with the hammer cocked (or cocked and locked). Some still don't pass

That's incorrect. Here's the Code for testing:

The weapon shall be dropped in the condition that it would
be in if it were dropped from a hand (cocked with no manual safety
applied)

http://www.leginfo.ca.gov/cgi-bin/displaycode?section=pen&group=31001-32000&file=31900-31910

 

[Vern Humphrey]

They don't have different amounts of energy. They have different amounts of kinetic energy on different vectors. Would you rather hit a car going the same direction as you, or in the oncoming lane? Does a car coming at you have more energy than a car driving next to you?

We’re not talking about cars in different lanes. We’re talking about two identical guns, both dropped the same distance, one cocked and one not cocked.

Explain how one gun is different from the other. Show the math.

 

[RX-79G]

We are talking about two guns that bounce, and whether the distance of the firing pin following those guns is going to change the their combined impact speed.

Gun with firing pin touching primer:

1. Gun and firing falling together at 9.8m/s down vector
2. Gun hits the floor and temporarily stops 0m/s down vector. Firing pin strikes at 9.8m/s and then stops, so now also at 0 down.
3. Gun bounces up at 4m/s up vector. Firing pin, still touching primer, also bounces up at 4m/s up vector.


Gun with gap between primer and firing pin.

1. Gun and firing falling together at 9.8m/s down vector
2. Gun hits the floor and temporarily stops 0m/s down vector. Firing pin continues down at 9.8m/s down vector. Velocity difference is now 9.8m/s.
3. Gun bounces up at 4m/s up vector. Primer finally comes in contact with 9.8m/s down vector firing pin. Combined velocity between up and down vectors is now 4+9.8=13.8m/s

13.8m/s greater than the maximum of 9.8m/s impact speed in the first example.


Is that enough math? I could graph that for you.

 

[Vern Humphrey]

1. Gun and firing falling together at 9.8m/s down vector
2. Gun hits the floor and temporarily stops 0m/s down vector. Firing pin continues down at 9.8m/s down vector. Velocity difference is now 9.8m/s.
3. Gun bounces up at 4m/s up vector. Primer finally comes in contact with 9.8m/s down vector firing pin. Combined velocity between up and down vectors is now 4+9.8=13.8m/s

In other words you assume that while the gun is overcoming it's momentum and starts it's upward motion, somehow the firing pin is in suspended animation, and only resumes its fall as the gun starts up?

 

[RX-79G]

Nope. I'm saying that the space between them allows the firing pin to continue to fall while the gun is rebounding. And the larger the gap, the more time there is for the gun's rebound to develop.

When there is little or no gap there is no time for the gun to reverse its vector before the firing pin catches up.

 

[Walt Sherrill]

The guns tested in California -- including 1911s --are NOT tested with the hammer cocked (or cocked and locked). Some still don't pass

That's incorrect. Here's the Code for testing:

The weapon shall be dropped in the condition that it would
be in if it were dropped from a hand (cocked with no manual safety
applied)

You're right. Hammer-equipped guns are dropped cocked and locked, with the safety not engaged. I apparently read right past that key bit several times -- and then used someone's summary when I made my earlier response.

In my defense there are three different places where this is addressed on the California website: the penal codes cited, Penal Code 12128, and "The Department of Justice Regulations for the Laboratory Certification and Handgun Testing Programs"; there are also summaries elsewhere and I must have picked the wrong one when I wrote the point that you corrected.

The gun and firing pin initially are going the same direction. Then the firing pin is moving and the gun is stopped. Then the gun is moving up and the firing pin may still be moving down.

Hitting a buttress is like hitting a car of the same mass head on at the same speed, but it is also like hitting a truck of twice the mass at half the speed. The gun has 100 times the mass of the pin. But that's only important if you want to know about what happens to the two things that impacted, but we are really only interested in what happens to the primer, and all we really need to know is what how fast the pin was moving relative to the primer.

"...may still be moving down."

I'm not sure that MASS matters in this discussion, nor velocity. The firing pin spring also has much greater mass than the firing pin -- but the firing pin still depresses it, somewhat. Although the firing pin spring is arguably still being depressed by the firing pin as the barrel and slide stop (but you've already told us THAT wasn't enough force to allow the firing pin to continue to the primer), the firing pin spring will also start to move and decompress, and release some of the force stored by the earlier firing pin hit.

You believe the BOUNCE explains what happens. You believe the firing pin spring is still moving toward the primer, and the spring is still being compressed. You might be right, but you've offered only theory and no evidence. Depending on just how far the firing pin spring has been compressed (by the firing pin strike AND by the spring's own inertia), it may be moving everything (including the firing pin) in the other direction. Is there any proof for either side of this discussion from any source, anywhere? You seem to be arguing that YOUR theory is better than anyone else's theory, but offer no evidence that such IS the case. It seems logical to you.

Wolff Springs will send along heavier firing pin springs when you buy a heavier recoil spring. It would seem that the Wolff is concerned (at least with gun without a firing pin safety) that there might be some risk of an inertial firing pin strike when a much heavier recoil spring is used. The force aren't the same, I know... but I don't know how much different they might be. A slam-fire and a drop don't seem that much different (to a physics-challenged layman.)

 

[Vern Humphrey]

Nope. I'm saying that the space between them allows the firing pin to continue to fall while the gun is rebounding. And the larger the gap, the more time there is for the gun's rebound to develop.

When there is little or no gap there is no time for the gun to reverse its vector before the firing pin catches up.

And that is true in BOTH CASES. If now, show calculations that demonstrate the time differential between firing pin strikes is adequate to make a significant difference.

 

[RX-79G]

What do you mean "show calculations"? I have no idea how long it take for the gun to rebound, and neither do you.

Up until now you didn't seem to even understand what I was talking about, and now you're taking a different tact by saying you don't think there is enough time? How do you have any idea if it is or isn't enough time?


I have an idea the distance matters because of which guns pass the tests and which do not. Do you have any math to explain that?

 

[Vern Humphrey]

I have no idea how long it take for the gun to rebound, and neither do you.

Then you cannot claim that one firing pin impacts BEFORE rebound, and the other AFTER rebound.

That means the SOLE difference in firing pin impact is due to the extra 0.1 inch one of the firing pin falls, and as I have shown the increase in kinetic energy is negligible.

 

[RX-79G]

Of course I can claim that two objects touching impact simultaneously, and two objects that with a space between them happen later.

That isn't complicated, that's the nature of time.


But to be specific, I am saying that the size of the gap is going to predict whether the impact is simultaneous, occurs when the pistol is momentarily motionless or after the bounce. And that's entirely reasonable. I just have no way of estimating what gap is going to produce what.


You have no grounds to say that the impact couldn't happen after the rebound. It isn't a question of whether it can happen, only how much gap it takes to make it happen. The fact that you can't see that as even a possibility has made discussing this with you really frustrating.



Which is surprising, since accepted my suggestion in the thread about blocking the bullet that max pressure wouldn't much exceed normal without requiring any math from me. Both are just possibilities based on observed effects.


Browning designed the inertial firing pins for hammer down carry drop safety. Presumably, they worked as designed in his workshop in that state. But they don't work when the hammer is cocked and dropped 1 meter. I've made my suggestion about why and went to some length to explain the same thing to you and Walt. I don't feel you are being particularly open minded about it.

 

[JTQ]

Browning designed the inertial firing pins for hammer down carry drop safety. Presumably, they worked as designed in his workshop in that state. But they don't work when the hammer is cocked and dropped 1 meter.

I'm not sure why you've come to that conclusion.

The Swartz firing pin safety was developed in the 1930's long before Condition 1 carry became popular. I'm pretty sure it wasn't developed simply as an engineering exercise to see if they could do it. There must have been a determination the gun was in need of such a device at the time.

 

[RX-79G]

That's a good question, but the Swartz safety might have been attractive because it prevented firing from half cock as well. Lots of people to this day don't understand how dangerous half cock is.

But it could have been for muzzle drops. That's just not the only possibility.


Here's an article about Swartz. He isn't specific about a particular danger:
http://www.m1911.org/technic12.htm

 

[JTQ]

It is a Swartz firing pin safety.

May the Schwartz be with you.

 

[Vern Humphrey]

Of course I can claim that two objects touching impact simultaneously, and two objects that with a space between them happen later.

What two objects touching?

Are you claiming that when the hammer is down on an M1911, the firing pin is touching the primer?

Take your M1911 and lock the slide back. Press the back end of the firing pin until it's flush with the firing pin stop (as if the hammer were fully down.) See if the tip of the firing pin sticks through the firing pin hole in the breech face -- it won't.

 

[RX-79G]

No, I'm comparing touching (Makarov), compressed inertial (usually within 1mm of the primer) and uncompressed.

Each of those is going to run into the primer at different points following the pistol hitting the ground. The distance from the primer (all else being equal) is going to determine how much after hitting the ground they will strike.

 

[Vern Humphrey]

Original Question:

So would a 1911 that would fail a CA drop test with the hammer cocked, pass if the hammer was down?

 

[RX-79G]

Vern, this is getting tiresome. Do you really not understand what is being discussed?



Yes, I think a 1911, in particular, might not discharge from 1 meter drop if decocked for all the reasons stated. And no, this isn't a 1911 only thread, and other guns that are similar or different can be referenced to illustrate the basics.

 

[Vern Humphrey]

Except you keep moving the goal posts -- when you say the firing pin rests on the primer, I point out that in the M1911 (which is the gun we're talking about, per the original post) it does not. Then suddenly you say we are talking about the Makarov.

Similarly, when you talk about the pistol rebounding, you talk as if the pistol does NOT rebound before the hammer-down firing pin strikes, but it DOES rebound before the cocked pistol firing pin strikes -- and then can show no calculations or proof that either case is true.

 

[RX-79G]

Vern,

I have attempted to use a variety of examples, mainly because YOU kept saying that the gun comes to a rest when it hits the floor and that the firing pin's falling distance was completely immaterial.

Now we're beyond the point of you insisting that that gun itself is immaterial, but you're holding me accountable for the countless explanations I had to offer you.


So I will go back to what I said right from the beginning, so you can't act confused:

To calculate the velocity you'd need the upward velocity of the gun as it bounces plus the initial velocity of the firing pin going down. If the firing pin starts closer to the primer there is less time for the guns upward velocity to develop before the pin hits.

Depending on the pin gap, it will strike simultaneous to the gun landing, just after the gun landed, or when it is bouncing up.


I don't have any fancy math, because the math wouldn't necessarily accurately reflect the reality of a steel gun bouncing off concrete. What I do have is a reasonable hypothesis and wanted to share it. Some people think it is quite possible, some think it is possible but unlikely, and some people don't understand.

If I could tell if you were in the unlikely or don't understand category, then we could have a discussion. But you appear to want to vacillate between those two and then make it sound like I am trying to make this complicated.

So I'll just ask: Do you think it is possible that a larger gap between pin a primer could increase the likelihood of firing because it gives the gun a chance to bounce?

And if it is possible, what amount of gap would you find likely to be a factor? If not 3mm: 5mm, 10mm, 25mm?

 

[Vern Humphrey]

We started with an M1911, let's stick with the M1911, so we're speaking the same language -- otherwise we'll wind up talking about revolvers or wheel locks.