Inertial firing pins - less drop safe hammer cocked?

Sounds reasonable.

I wonder in an unlocked 1911 would fire at all under that condition, or if the slide would not go out of battery and absorb most of the impact force in the process. A cocked and locked series 70 gun could fail as you described, but uncocked also means unlocked.

If I'm climbing a ladder, I'll just choose my Glock (striker safety block) instead of my 1911. Problem solved. You can always choose an even lighter FP or a stiffer FP spring for more inertia safety. Even a retention strap on your holster.

Being that I care about my safety, I actually tested this with a turdy Kimber with the shwartz removed and a blank. It's nearly impossible to get a 1911 to go off by dropping it. Mine would not. Had to recrown the barrel and refinish the slide.

An additional 0.1" of firing pin travel, under the influence of gravity would yield about 1 fps additional velocity. I don't think hammer cocked or hammer down would make a difference. A stiffer firing pin spring would easily prevent accidental discharges from any reasonable drop distance.

So:

Assuming a 1911 can fall exactly on it's nose and the concrete stops it immediately.

-how much does the FP weigh?
-how much force does it require for a decent FP spring to compress?
-how much force does it take to dent a primer?

-how far do I have to drop a 1911 to get enough momentum in the firing pin to overcome the spring force and the force required to activate the primer?

Would be a fun, if simple, physics problem for the kids.

Not following your math. It isn't one gravity. 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.

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First of all, the question I'm addressing was not "how fast and how much does the gun rebound?" It was "Does the firing pin have significant additional velocity if the hammer is cocked, versus hammer down on the firing pin?"

Assuming the firing pin to weigh .01 lbs, then the additional energy of the firing pin from a 0.1 inch additional fall would be negligible -- virtually too small to measure.

Vern, I am not following how you are getting a velocity from a distance alone. Velocity comes from acceleration over a distance, and you don't have an acceleration number. It isn't gravity, but comes from the actual velocity the gun hits with and then bounces up with.

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First of all, the gun and firing pin ARE falling by gravity, so the Gravitational Constant, 32.2 f/s/s holds.

Secondly the question was is there a significant difference between dropping the gun with the hammer cocked versus with the hammer down.

The gun will not rebound FASTER based on the position of the hammer, now will it?

Therefore the answer is to calculate how much additional velocity the firing pin would have with an extra 0.1" fall.

All I was getting at was that starting with the pin closer to the primer gives less time for a major velocity delta to develop

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And the calculations show there is no major velocity delta – unless you call one foot per second a “major” velocity delta. And, given the low mass of the firing pin, there cannot be a “major” energy delta, either.

In other words, hammer down or hammer cocked, makes no significant difference.

First of all, the question I'm addressing was not "how fast and how much does the gun rebound?" It was "Does the firing pin have significant additional velocity if the hammer is cocked, versus hammer down on the firing pin?"

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I don't see how the hammer being cocked or NOT cocked makes any difference... as it's the firing pin itself that is moving inertially -- the hammer isn't really a big factor. (And being cocked would mean the hammer would have to overcome the sear that is in the way.)

As is clear from my following comments, I have only a rudimentary understanding of physics, but it seems that the key factors at play are:

1) how far the firing pin must travel to contact the primer with enough force to ignite the primer;

2) the nature of the primer itself (as some are "harder" to ignite than others);

3) the ability of the firing pin spring to resist the inertial movement of the firing pin; and

4) how far the gun must drop to make the firing pin (step 1, above) move enough to ignite the primer (step 2).

As others have noted -- things fall at the same rate regardless of their weight -- so the weight of the firing pin (wind resistance isn't a factor) -- shouldn't play much of a role.

• The weight of the firing pin spring (it's measured strength to resist the firing pin when it's struck by the hammer, not it's actual [physical, material] weight) MIGHT be a factor.
  
• It seems as though the shape/size of the firing pin tip could play a small role in terms of passing the inertial force to the primer, but I know ZILCH about primers and how they work, so that may be irrelevant.

Seems as though all of those variables can change from event to event, and there are too many variables at play to make a general statement -- except when talking about 1911s without a firing pin block that are made to a general standard, like those that consistently fail CA drop test.

The important acceleration is not that of gravity. The important acceleration is the rebound acceleration off the floor.

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The question does not address rebound acceleration. It ONLY addresses the difference between the hammer down or hammer cocked.

RX-79G said:

The hammer is a factor because when it is lowered it decreases the distance between the pin and the primer by pushing the pin into the slide, which you mention in 1).

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OK. That makes sense, but it can't have MUCH of a role (albeit SOME).

The part I was responding to was slightly different, when the poster asked:

Does the firing pin have significant additional velocity if the hammer is cocked, versus hammer down on the firing pin?

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Hammer cocked ought not have any effect on the firing pin. Hammer down? Maybe. Using your argument, things would change slightly: the distance the firing pin would have to travel would be slightly less, and the firing pin itself would meet likely meet a bit less resistance from the slightly compressed spring (which has been a bit compressed by the hammer) -- but I wouldn't know how to GUESS the effects of those changes. One factor (shorter distance to travel) MIGHT somewhat offset the other (less resistance to overcome.)

We've got to be careful here, or we'll end up acting like a group of medieval clerics arguing about how many angels can dance on the point of a pin...

(If the angels are at all like some of the very religious Protestants I've known, they probably don't dance... )

And by my calculations, which consider the firing pin to be a free falling object, the hammer back state would result in about 1 fps in additional velocity for the firing pin. That translates into an almost undetectable increase in kinetic energy.

And in answering the original question, it doesn't matter WHAT the impact velocity is -- what matters is how much FASTER is the pin from the cocked gun than from the gun with the hammer down.

In SF training we were taught that the Makarov isn't drop safe and should always have the safety engaged when a round is in the chamber.

RX-79G said:

I'm pretty sure the mass and velocity of the firing pin is not primarily what makes dropped guns fire. A pistol that will fire when dropped from 1 meter, as in the CA test does not have a firing pin that would ignite a primer if dropped from 1 meter with a spring on it. The pin wouldn't even touch the primer.

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I found the following on the net, re the CA drop test. Here's a link http://oag.ca.gov/sites/all/files/agweb/pdfs/firearms/regs/chapter5.pdf. See page 6 for specifics:

12128. As used in this chapter, the "drop safety requirement for handguns" means that at the conclusion of the firing requirements for handguns described in Section 12127, the same certified independent testing laboratory shall subject the same three handguns of the make and model for which certification is sought, to the following test:

A primed case (no powder or projectile) shall be inserted into the chamber. For pistols, the slide shall be released, allowing it to move forward under the impetus of the recoil spring, and an empty magazine shall be inserted. For both pistols and revolvers, the weapon shall be placed in a drop fixture capable of dropping the pistol from a drop height of 1m + 1cm (39.4 + 0.4 in.) onto the largest side of a slab of solid concrete having minimum dimensions of 7.5 X 15 X 15 cm (3 X 6 X 6 in.). The drop distance shall be measured from the lowermost portion of the weapon to the top surface of the slab. The weapon shall be dropped from a fixture and not from the hand. 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). If the design of a pistol is such that upon leaving the hand a "safety" is automatically applied by the pistol, this feature shall not be defeated. An approved drop fixture is a short piece of string with the weapon attached at one end and the other end held in an air vise until the drop is initiated.
The following six drops shall be performed:

(a) Normal firing position with barrel horizontal.
(b) Upside down with barrel horizontal.
(c) On grip with barrel vertical.
(d) On muzzle with barrel vertical.
(e) On either side with barrel horizontal.
(f) If there is an exposed hammer or striker, on the rearmost point of that device, otherwise on the rearmost point of the weapon.​

The primer shall be examined for indentations after each drop. If indentations are present, a fresh primed case shall be used for the next drop.

The handgun shall pass this test if each of the three test guns does not fire the primer.​

Apparently, some guns do ignite primers with the spring installed. But a lot of guns aren't even submitted for testing... because the gun makers don't want to give up three handguns that are unlikely to pass the tests.

Vern Humphrey said:

And by my calculations, which consider the firing pin to be a free falling object, the hammer back state would result in about 1 fps in additional velocity for the firing pin. That translates into an almost undetectable increase in kinetic energy.

And in answering the original question, it doesn't matter WHAT the impact velocity is -- what matters is how much FASTER is the pin from the cocked gun than from the gun with the hammer down.

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Didn't you say the difference is almost undetectable? According to info on the 'net, most states who do drop tests don't test with the hammer cocked.

Back to RX-79G's comments:

The California drop test requires that the gun be dropped with any user-managed SAFETY mechanisms not engaged. CA doesn't test cocked and locked 1911s with the safety on; only with the safety off.

It's not clear, from reading their documentation whether they test with the hammer down or back, but I suspect they do both. They certainly drop them in a lot of different ways, including upside down, sideways, flush, less than flush...

I'll say it again: I have only a rudimentary understanding of physics, but...

Whether 1) the inadvertent movement of the firing pin is due to inertia when the gun first hits the concrete or 2) whether the primer strike is the consequence of the gun and barrel bouncing against the firing pin after hitting the concrete, I would argue that the cause is the same. If the firing pin doesn't move forward (in relative terms), the primer isn't going to be struck.

When the gun first hits, it stops -- but the firing pin and firing pin spring don't. Rebound acceleration was mentioned somewhere here. Aren't the firing pin spring and firing pin also going to rebound, too -- after a split second delay? And can't that second rebound also reduce the likelihood of the pin closing the gap? (The force already stored in the spring might also be pushing the firing pin away from the primer as the barrel and slide bounce...)

If the gun barrel and slide hit flush against the concrete the whole slide assembly should move as a unit -- and only the firing pin (and firing pin spring) can move. If the firing pin travel is a consequence of the barrel and slide bouncing, the firing pin must still move, in relative terms, for the primer to be struck. But it gets more complicated if the rebound is where things happen.

If the barrel and slide hit at a slight (or greater) angle, the barrel can/might unlock or begin to unlock from the slide and if the primer hasn't already been struck, the gap between breech face and primer can increase. But the firing pin can still move forward. CA doesn't test for this "off-vertical" hit, so it might suggest they don't consider it a risky issue.

RX-79G said:

What causes guns to fire when dropped is the gun bouncing up into the pin, not the pin running into a suddenly stopped pistol. The bouncing is why the distance to the pin matters.

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Given that the pin has to have moved through the breech face and be there with some force, I don't know HOW the barrel is going to bounce into the firing pin! Particularly if the pin movement is retarded by the firing pin spring. Given my meager understanding of physics, it seem to me that the firing pin's ability to jump of the gap is most likely to occur at the moment of impact (with a flush hit), rather than later... when the barrel must bounce against a firing pin that may also be bouncing as IT rebounds!!

Maybe someone can explain the other ("rebound") possibility in a way that makes sense to us who are "physics"-challenged.

.

RX-79G said:

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.

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NO. That is incorrect. The firing pin does all its acceleration while the gun is falling. What happens at muzzle-down ground impact is that the barrel decelerates essentially instantly, and the firing pin continues moving. While it moves, it is decelerating because the FP spring is working to slow it, but it may or may not have enough energy left by the time it reaches the primer to pop it.