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Thread: Series 70 drop tests

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  1. #11
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    You guys raise an interesting point. With that in mind ponder this. What if the firing pin isn't the issue here?

    After thinking about it a bit, you are correct about the firing pin. The increased force is in the slide/barrel/frame assembly. To use an analogy, if you hit a concrete block with a 12oz ball peen you will get a different result than if you hit it with a 5lb sledge hammer.

    When the muzzle impacts the concrete surface an equal and opposite force is being applied to the barrel and slide in the opposite direction correct? So could the force of the impact be driving the barrel (and the captured cartridge) back into the breechface and firing pin with sufficient force to achieve something akin to a slam fire?
    "The 1911 was the design, given by God to us through John M. Browning, that represents the epitome of what a killing tool needs to be. It was true in 1911 and it's true now." - Col. Robert Coates commanding, U.S. Marine Corp Special Operations Command Detachment 1 (DET 1)

  2. #12
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    Quote Originally Posted by garrettwc
    When the muzzle impacts the concrete surface an equal and opposite force is being applied to the barrel and slide in the opposite direction correct? So could the force of the impact be driving the barrel (and the captured cartridge) back into the breechface and firing pin with sufficient force to achieve something akin to a slam fire?
    No.

    Go back to the formula you cited: F = M x A

    When the assembly is dropped (regardless of whether it's a complete pistol or just a slide & barrel), the acceleration is produced entirely by gravity, at a rate of 32 feet/second/second. If the firing pin were simply held inside an oversized tube and both the pin and tube released at exactly the same instant, both parts would still accelerate at the same rate and strike the ground at the same instant.

    So we have a captive firing pin in a hollow tube, surrounded by a hunk of metal. Let's say it achieves a velocity of 32 feet-per-second before it hits the concrete.

    If the concrete and the barrel were both infinitely hard, the slide/barrel assembly would stop instantly. In fact, that's impossible, because to do so would require negative acceleration equal to infinity. But, the gun or the barrel/slide assembly do stop VERY quickly ... meaning very rapid negative acceleration.

    But the firing pin is restrained only by the pressure of the firing pin spring (and to a slight degree by friction in the firing pin bore). It keeps moving as the slide stops. This is, in effect, the same physics as a slam fire, but not because the barrel is driven back in the slide. It's a locked breech pistol, remember? If the barrel can be driven back far enough and with sufficient force to cause a detonation ... the barrel lugs are sheered off AND the barrel hood is missing.
    Hawkmoon
    On a good day, can hit the broad side of a barn ... from the inside

  3. #13
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    Ah yes, I forgot about the locking lugs. I was thinking the slide would still have some forward travel even though the barrel had stopped, but I see where you're coming from.

    I was thinking about this comment from Mr. Oldham:
    The thumb safety was left OFF as preliminary testing with the safety ON indicated that damage to the thumb safety, slide, and plunger tube would occur with only a few drops.
    I pondered that anything moving backward with enough force to damage the thumb safety could cause it. So I guess the ultimate question becomes how long and how far does the firing pin move after the slide/barrel stops and starts moving rearward?

    And further, if the test were repeated with a series 80 setup, would we see any sort of peening on the FPS? Based on the theory, the FPS should be banged up pretty good on one side.
    "The 1911 was the design, given by God to us through John M. Browning, that represents the epitome of what a killing tool needs to be. It was true in 1911 and it's true now." - Col. Robert Coates commanding, U.S. Marine Corp Special Operations Command Detachment 1 (DET 1)

  4. #14
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    Quote Originally Posted by Hawkmoon
    Impossible unless you suspend at least two fundamental laws of Physics.

    Essentially, you are saying that if you are a passenger in a car and the car rams a HUGE concrete bridge abutment, your head will hit the dashboard harder if you're in a heavy car than if you're in an econo-box.
    Actually, if you were in the econo-box, your head would hit the abutment cause the car would fold easier.
    Although it would not be an even comparison, you have 2 hand guns, a 9mm shooting 115 grain bullet and a .45 shooting 230 grain bullet.....each at a velocity of 850 fps.....which one would be more likely to knock down a steel plate at 20 yards? Kinetic energy comes into play here somehow....
    Drop a bowling ball and a baseball from 10 feet on someones head...I guarantee there won't be any grey matter on the baseball.
    I dunno Hawkmoon...I just may be too thick-headed to understand.
    Beauty is skin deep but ugly goes right to the bone.

  5. #15
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    For those interested in a glimpse of how we did it, here's a YouTube clip:


    This is just an example. The pistol was hung from an eyebolt, run up to the desired height (we drew a scale on the garage door) and dropped as you see it. There was no restraint on the pistol once it was released. The magazine was present and full (of dummy rounds). Here's a pic:


    One consideration that just came to me was the rebound of the pistol as it bounced off the ground. That is, the pistol was going back up (even if only slightly) whilst the firing pin was on the way down. That action would not increase the energy in the firing pin (which is the usual figure of merit when considering firing pin/primer interaction), though it would add to the total energy in the firing pin/primer system.

    For an example of the considerations involved in firing pin energy and primer sensitivity, please see The Black Rifle by Stevens and Ezell, pages 132-144.

    Regards,

    Walt
    Author, The M1911 Complete Assembly Guide,
    The M1911 Complete Owner's Guide, NEW The 10/22 Complete Owner's and Assembly Guide,
    The M14
    and M1 Garand Complete Assembly Guides
    and The AR-15 Complete Assembly and NEW Owner's Guides
    Last edited by wjkuleck; 24th November 2010 at 15:26. Reason: Added Still Picture


  6. #16
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    Outstanding Walt! I didn't know you were involved with the test (although I'm not surprised). I had seen the still photos but not the actual drop.

    Quote Originally Posted by wjkuleck
    One consideration that just came to me was the rebound of the pistol as it bounced off the ground. That is, the pistol was going back up (even if only slightly) whilst the firing pin was on the way down. That action would not increase the energy in the firing pin (which is the usual figure of merit when considering firing pin/primer interaction), though it would add to the total energy in the firing pin/primer system.
    Sort of like whiplash? Interesting theory.
    "The 1911 was the design, given by God to us through John M. Browning, that represents the epitome of what a killing tool needs to be. It was true in 1911 and it's true now." - Col. Robert Coates commanding, U.S. Marine Corp Special Operations Command Detachment 1 (DET 1)

  7. #17
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    I was discussing a drop test with a guy who'd decided to do his own, but gave up when he determined that a 1911, if dropped, will not land on its muzzle. One of those unintended consequences deals, where everyone is concerned about mass, momentum, and gravity, while ignoring the validity of a test that starts from the assumption that a dropped gun will (ever) land on the muzzle. It would be like testing to see if a penny will drop between the boards in the deck in my back yard; yes, the penny is thinner than the gap between the boards, but I could drop a thousand pennies, and not one . . . oh, never mind.
    "A grip safety is just another excess moving part. I have never known one to prevent an accident, and moreover, it is difficult to postulate a circumstance in which it might." Jeff Cooper

  8. #18
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    Validity???

    Gentlemen,
    I have had several people ask me about the results of my tests. Two of these people are highly respected 1911 smiths that have had different results than mine. Bottom line is this. I dropped an Auto Ordinance and a custom Caspian and received similar results. My functional 1911's, without a firing pin block, will fire when dropped from certain heights onto certain types of flooring. These tests were conducted without bias and are able to be duplicated. I published the results for the benefit of the 1911 community and the persons that carry the 1911.

    Drake

  9. #19
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    Drake, thanks for your efforts, sincerely appreciated.

    I guess what we are trying to figure out, is why different testers get different results on this issue. It would be really interesting if you guys had access to a hi-speed video camera, since in Walt's video, it's impossible to see the exact moment the pistol hits the ground.
    John Caradimas SV1CEC
    The M1911 Pistols Organization
    http://www.m1911.org
    Last edited by John; 25th November 2010 at 03:57.


  10. #20
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    Nice work Drake.

    Perhaps tests like these will dispel more long time and often repeated "myths" about the 1911 drop safety.
    Something even Colt knew or suspected in the 1930's, and all the 1911 manufacturers "know" because they modify their 1911s for the California drop test for only a "measly" 39" drop test.

    I am surprised the 45 steel firing pin went "off" at such a short distance however!

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