Safety ON, Revisited.

[halfmoonclip]

Early centerfire revolvers were made safe by lowering the hammer on an empty chamber, but the notion of a 'rebounding' hammer came along in the 19th Century. Rebounding hammers retreat from the full forward position when the trigger is released. Smith 'Lemon squeezers', an early effort at a foolproof revolver, had a rebounding hammer, a grip safety, and a trigger pull from hell. Later Smith revolvers (say, an '05 M&P) had a rebounding hammer which was prevented from going forward if struck by a protrusion on the hammer which interfaced with another raised area on the rebound slide, which is linked with and powers the trigger. As long as the trigger is forward, the hammer is held away from the primer...unless, as Mike noted, the thing was dropped from a great height, landing hard enough on the hammer to break the hammer axle. This is a 1/4" stud pressed into the left side of the frame and supported on both ends; the hammer turns on it. To prevent this from reoccurring, Smith went to a hammer block that is cammed out of the way by the rebound slide when the trigger is pulled.
Unless some fool is determined to play the drum solo from 'Gadda da Vida' on the hammer spur with an 8oz ball peen, I find it hard to picture how the hammer block could be beaten 'paper thin'. Sorry, Mike, but that's a reach and not likely to occur in the real world, especially since the old system of blocking hammer movement with the rebound slide is still in place on current Smith production.

I also recall the HP White lab tests, but don't recall the results. Either they were favorable to the guns tested, or the NRA/gun industry put the kibosh on them. The administration at the time (Kennedy? Johnson?) wanted to identify 'unsafe' guns (Saturday Night Specials?) as contrasted to quality firearms, as a means to ban the former. Again, as I recall, the current arrangement where the Consumer Product Safety Commission has no say about firearms is related to this issue. The concern, of course, was that the CPSC could ban every gun with the stroke of a pen, claiming it 'unsafe'.

I'll be interested in reading some more of Iron Man's physics; it does seem that you would have to be living really wrong to get a discharge when dropped from waist height. The Bond movie where James manages to fumble his gun and drop it several stories is a more believable scenario. Some pistols now use a titanium firing pin; its light weight makes an inertial discharge about impossible even if the gun was dropped from Mars. What I would really like to know is just how great the risk actually is with a traditional steel firing pin without a block. It may well be that the gun industry is just covering their derriere.
Moon

[MGMike]

I have been spending 'way too much time on the forum in the past week because I have been sick in bed and didn't feel like doing much of anything else. But I am now feeling fairly human again and have to return to more productive pursuits.

For that reason I am going to make an exit from point-by-point refutations and extended discussions of everybody's theories and opinions -- some of which, at least, seem to be based from what can or cannot be found on the internet.

What I have written in this and other threads recently regarding drop-firing and other mechanical failures are not figments of an overactive imagination. They are drawn from knowledge of real-life testing and actual incidents that have occurred. You are all free to take caution from them or not as you please.

Anyone interesting in pursuing the topic would do well to first sit down and study the test procedures and criteria of SAAMI, the BATF, the H.P. Laboratory and the German Police Academy (which are all different). That's not everything one needs to know, but it's a start.

M

[Iron Man]

Mike,

I am not attempting to argue or insult. I am curious about the tests so that I can read them as I could not find the test results online. I was simply saying the physics don't make sense. Almost all handgun manuals caution against dropping a loaded firearm. However, for a small firing pin to gather enough momentum to overpower the spring and still set off a round would require a much greater than average height.

I responded in the middle of the night and where I live published research from firearm testing companies are not readily available even during normal hours.

[MLB]

I'd heard of the use of titanium firing pins as a method of reducing the mass (and therefore the inertia) in the case of a dropped firearm. Seemed a bit hokey in my first impression. Such a tiny piece of metal can't have much of a difference in weight.

Titanium has a density approximately 60% that of steel though. (I say approximately, since I don't know what alloy of Ti is used, and "steel" is an alloy of iron. I used Ti metal and medium carbon steel. Reference Online Materials Information Resource - MatWeb for data.) Regardless, it is a significant difference in density. I'd expect a proportional reduction in impact energy at the primer.

Just a few rambling thoughts...

[halfmoonclip]

Originally Posted by MLB

I'd heard of the use of titanium firing pins as a method of reducing the mass (and therefore the inertia) in the case of a dropped firearm. Seemed a bit hokey in my first impression. Such a tiny piece of metal can't have much of a difference in weight.

Titanium has a density approximately 60% that of steel though. (I say approximately, since I don't know what alloy of Ti is used, and "steel" is an alloy of iron. I used Ti metal and medium carbon steel. Reference Online Materials Information Resource - MatWeb for data.) Regardless, it is a significant difference in density. I'd expect a proportional reduction in impact energy at the primer.

Just a few rambling thoughts...

MLB, I have a couple pistols with the Ti pins, and they have worked just fine; impact on primers does not seem affected. It seems a more elegant solution to me than the numerous linkages and plungers (with their attendant possibilities for mischief) necessary for a firing pin lock. As I noted, said linkages can have an adverse effect on trigger pull as well.
Perhaps fitting in with Iron Man's research, it may not take much of a reduction in mass to solve any dropfire question.
Moon

[lawabiding]

Originally Posted by Iron Man

... a hammer exerts energy based upon the square of the hammer mass times its velocity divided by two ...

I usually find it difficult to evaluate comments like this, because most of us use common terms that we assume mean the same thing to different people, even though they sometimes do not. For example, the phrase "exerts energy" is seldom if ever seen in the standard literature. A body may have energy of a certain type, depending upon its position, speed, or some other measure. Further, a body may transfer energy in various ways. However most usually in physics, force rather than energy is "exerted."

In the present example, I assume you are referring to the kinetic energy of the hammer. If so, you state that the kinetic energy can be calculated as:

E = [(m) x (m) x (v)]/2

where m is the hammer mass and v is the hammer velocity. However in standard mechanics, the actual formula is:

E = [(m) x (v) x (v)]/2

which is quite different from what you wrote. Note also that this formula is specific for non-rotating objects, and since the hammer is constrained to rotation about it own fulcrum, we are actually dealing with an entirely different case.

Was this a typo?

[Iron Man]

Originally Posted by lawabiding

I usually find it difficult to evaluate comments like this, because most of us use common terms that we assume mean the same thing to different people, even though they sometimes do not. For example, the phrase "exerts energy" is seldom if ever seen in the standard literature. A body may have energy of a certain type, depending upon its position, speed, or some other measure. Further, a body may transfer energy in various ways. However most usually in physics, force rather than energy is "exerted."

In the present example, I assume you are referring to the kinetic energy of the hammer. If so, you state that the kinetic energy can be calculated as:

E = [(m) x (m) x (v)]/2

where m is the hammer mass and v is the hammer velocity. However in standard mechanics, the actual formula is:

E = [(m) x (v) x (v)]/2

which is quite different from what you wrote. Note also that this formula is specific for non-rotating objects, and since the hammer is constrained to rotation about it own fulcrum, we are actually dealing with an entirely different case.

Was this a typo?

Yes, it was indeed a typo. I meant to write "mass times velocity squared divided by two." The calculations were correct, but I did indeed state it incorrectly. It was the middle of the night...I'm glad I don't have to take tests at that time.

[highlandmac]

I actually experienced an accidental discharge... My PPK/s fired once during a jam. Broken spring in the magazine caused two shells to lodge in the slide/chamber, when I dropped the magazine the slide went to battery, causing the hammer to drop and discharged the round in the barrel. No one hurt, I was outside on my farm but still a little un-nerving. I will say, I was a little leary of carrying the Walther again until I ran it thru several test and was never able to replicate the same problem again. I now only use Walther magazines, springs and round nose ammo, no hollow points......