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Thread: ND in an MRI

  1. #1
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    Found this on the Hi Point forum...Long read, but still a good one. I wonder who's doing their research....1991A1?!?!?!? BLASPHEMER!!!!!!!!!!!

    http://www.ajronline.org/cgi/content/full/178/5/1092

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    An incident recently occurred at an outpatient imaging centerin western New York State, in which a firearm spontaneouslydischarged in a 1.5-T MR imaging environment with active shielding.To our knowledge, this is the first documented case of suchan occurrence. The event confirms previously reported theoreticrisks of a firearm discharging in an MR imaging environment [1].In this report, we examine the incident in detail from the officialpolice and ballistic reports.
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    An off-duty police officer went to an outpatient imaging center(not affiliated with our institution) in western New York Stateto have an MR imaging examination. The facility housed a 1.5-TMR unit (Signa; General Electric Medical Systems, Milwaukee,WI) with active shielding. The officer was carrying a model1991 A-1 compact.45 caliber semiautomatic pistol (Colt's Manufacturing,Hartford, CT).
    The officer notified the technologist that he was carrying theweapon before entering the MR dressing room. The technologisttold the officer to take the gun with him. The technologistintended to meet the officer in the MR patient waiting areabefore the examination and secure the weapon in that room, wherehe felt it would be safe. However, the officer apparently misunderstoodand took the gun into the MR suite. The technologist was enteringthe officer's personal data into the computer and did not seehim entering the MR suite.
    Once the officer was inside the MR suite, the gun was pulledfrom his hand as he attempted to place the gun on top of a cabinet3 ft (0.9 m) away from the magnet bore. The gun was immediatelypulled into the bore, where it struck the left side and spontaneouslydischarged a round into the wall of the room at the rear ofthe magnet. Fortunately, no one was injured. Although the gun struckthe magnet bore, only minimal cosmetic damage occurred to themagnet itself. The MR unit had full functional capability immediatelyafter the gun discharged. The weapon's thumb safety was reportedlyengaged when the gun discharged.
    An unsuccessful attempt to remove the gun from the magnet resultedin the gun being pulled to the right side of the magnet (Fig. 1).The decision was then made to power down the magnet to removethe gun.
    Fig. 1. Photograph shows gun (arrow) stuck on right side of MR imaging magnet bore.

    Examination of the weapon by a ballistics laboratory concludedthat the force of the magnetic field was responsible for thefirearm's discharge. To understand how the gun discharged requiresa brief discussion of the firing mechanics of the Colt 1991A-1.45 caliber pistol and the weapon's safety mechanisms [2].When the weapon is normally fired, the trigger is pulled, whichreleases the sear. The sear, in turn, releases the hammer. Thehammer then moves forward to strike the firing pin, which movesforward to strike the primer of the chambered round.
    The Colt 1991 A-1 pistol has three safety mechanisms (Fig. 2A,2B,2C,2D), includinga thumb safety, grip safety, and firing pin block. The thumbsafety locks the sear in place and prevents the hammer frommoving forward when the trigger is pulled. The thumb safetyalso locks the slide in place. The thumb safety is the weapon'sonly active safety mechanism; it must be turned on in orderto work. The grip safety is located at the back of the gun handleand prevents the trigger from being depressed. The grip safetyis a passive mechanism; it is always on unless deactivated.To deactivate it, the grip safety must be depressed at the sametime the trigger is depressed; otherwise, the trigger cannotbe pulled. The firing pin block is a small metal block, approximatelythe size of a pencil eraser, that sits in the firing pin channel andprevents the firing pin from moving forward. The firing pinblock is held in place by a small spring. When the trigger ispulled, a series of levers cam the firing pin block up intoits own well within the slide to allow the firing pin to movefreely within its channel.
    Fig. 2A. Photographs of 1991 A-1.45 caliber semiautomatic pistol (Colt's Manufacturing, Hartford, CT). Actual gun involved in incident is shown.
    Fig. 2B. Photographs of 1991 A-1.45 caliber semiautomatic pistol (Colt's Manufacturing, Hartford, CT). Muzzle of gun shows small amount of white paint (arrow) where gun impacted magnet.
    Fig. 2C. Photographs of 1991 A-1.45 caliber semiautomatic pistol (Colt's Manufacturing, Hartford, CT). Hammer, thumb safety, and grip safety of gun are shown. Gun is in cocked and locked position with hammer cocked and thumb safety turned on to prevent hammer from striking firing pin. This is condition in which gun was recovered from magnet.
    Fig. 2D. Photographs of 1991 A-1.45 caliber semiautomatic pistol (Colt's Manufacturing, Hartford, CT). Disassembled gun with view of slide interior from below shows firing pin block.

    At the time the weapon discharged, it was reportedly in a cockedand locked position; that is, the hammer was cocked and thethumb safety was engaged to prevent the hammer from strikingthe firing pin. A live round was in the chamber. (Many peoplewho choose this weapon for personal protection will carry itin this manner because it allows them to quickly fire the weaponif needed.)
    When the firearm was removed from the magnet, the gun was stillin a cocked and locked position. An empty cartridge was foundin the chamber. The presence of an empty cartridge in the chamberis highly unusual. If the thumb safety were not engaged andthe weapon fired normally by depressing the trigger, the normalbackward recoil of the slide should have automatically ejectedthe empty cartridge, and a new live round should have automaticallybeen chambered. As discussed earlier, the thumb safety performstwo functions: it prevents the sear from releasing the hammer,thereby preventing the hammer from striking the firing pin;it also locks the slide in place, preventing retrograde motionof the slide and automatic ejection of the empty cartridge. Thus,the presence of an empty cartridge in the chamber confirms thatthe thumb safety was engaged at the time the gun was fired.Given that the thumb safety was engaged when the gun discharged,it is also likely that the normal trigger and hammer mechanismof firing the gun was bypassed because the thumb safety wouldhave also prevented release of the hammer.
    The gun likely discharged as a result of the effect of the magneticfield on the firing pin block. The firing pin block was probablydrawn into its uppermost position by force of the magnetic field.The firing pin block has to overcome only light pressure froma relatively small spring to release the firing pin. The pistolwas likely drawn into the magnetic field so that the muzzlestruck the magnet's bore first. With the firing pin allowedto move freely in its channel, the force of the impact on themuzzle end was sufficient to cause the firing pin to overcomeits spring pressure and move forward to strike the primer ofthe chambered round.
    This account explains how the weapon discharged when the thumbsafety was engaged.
    The presence of an empty cartridge in the chamber explains whythe gun did not discharge a second time when it was moved fromthe left to the right side of the bore. Even if the identicalforces were repeated, an empty cartridge, not a live round,was in the chamber at this time.
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    In this incident, the gun discharged despite the thumb safetybeing engaged. This has important implications in that it showsthat the weapon poses a risk for discharging in an MR imagingenvironment even with the thumb safety engaged.
    One can look at the sequence of events preceding the dischargeof the weapon and see several points at which the incident couldhave been prevented. When the officer came in with the gun,it should have been immediately secured in a safe location,even before the officer changed for the examination. The technologist,knowing the officer had a firearm, should have instructed him thatunder no circumstances could he bring the weapon into the MRsuite. Also, the technologist should have been monitoring theofficer more closely to make sure he did not enter the MR suitewith the weapon. Signs should have been posted at that site,if they were not already there, warning the public of the dangersof approaching the magnetic field of the MR imager with implants, metallicdevices, or objects such as firearms.
    In light of this incident, all radiologists should reexamineour own site's screening methods to ensure that steps are implementedto prevent such a situation from ever recurring.


  2. #2
    Regular Member compmanio365's Avatar
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    Hehe, read this over on the Hi Point forum too.......what a tool for bringing his gun into an MRI......no noticing the HUGE signs saying "No metal objects"? He couldn't even claim he thought his gun was plastic, since he wasn't carrying a Glock. :P

    But it does prove just how safe the 1911 is.........the safety never came off, the hammer never moved, the slide never cycled........the only reason it fired was because of the firing pin block safety not being strong enough to overcome the magnetic force against it. Any gun would have had the same issue.

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    http://opencarry.mywowbb.com/view_to...;highlight=mri

    Dated 2006

    In the years past, no one has said that the primer was dimpled. EMF heating of the cartridge/primer is a more straight forward explanation.

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    Regular Member ODA 226's Avatar
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    I'm going for an MRI of my right shoulder next week. I'll make sure I leave my Springfield with my wife! LMAO!
    Bitka Sve Reava!
    B-2-10 SFG(A)/ A-2-11 SFG(A) 1977-1994

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    Campaign Veteran deepdiver's Avatar
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    compmanio365 wrote:
    ...the only reason it fired was because of the firing pin block safety not being strong enough to overcome the magnetic force against it. Any gun would have had the same issue.
    If the posted analysis is correct rather than Doug's hypothesis, it was not only the firing pin block moving, but also inertial forces from the gun flying out of his hand and into the MRI, with the muzzle pointing in the direction of travel thereby giving the firing pin the inertia required to strike the primer. If it's momentum had been sideways and back rather than forward I would think it would not have happened. Truly a freak occurrence.

    "Any gun" would not have this issue in such a freak occurrence. XD and Glock strikers are physically held in place against the striker spring force by the sear and the sear in turn is physically connected to the trigger via the trigger bar making them near impossible to set off without pulling the trigger even if dropped from several stories. I'm guessing this would be true at least to some extent for all striker fired weapons as that is the means of giving the striker the inertia otherwise given by the hammer fall. However, I am not familiar with other striker fired handgun internals to verify.
    Bob Owens @ Bearing Arms (paraphrased): "These people aren't against violence; they're very much in favor of violence. They're against armed resistance."

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    So, just make sure to bring one of them "plastic guns" to an MRI

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    At an average price of 6-10 million Dollars ( U.S.) for MRI machinery, its safe to say that the officer in question was VERY fortunate he got away with minimal cosmetic damage to the machine....a bit of Bondo &Krylon should fix this little boo-boo.

    On A More serious note.....it is very fortunate indeed that the only damage was to the MRI and not another person.

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    Doug Huffman wrote:
    http://opencarry.mywowbb.com/view_to...;highlight=mri

    Dated 2006

    In the years past, no one has said that the primer was dimpled. EMF heating of the cartridge/primer is a more straight forward explanation.
    But why would only the chambered round fire then? Wouldn't the entire magazine have gone off too?

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    Good point.

    I looked at http://www.ajronline.org/cgi/content...78/5/1092/FIG2 to see if the magazine was still with the gun.

    In re-reading the URL it appears that the field was on when the Pt and gun entered the suite and that the gun was influenced by the field only when the Pt placed it on a cabinet a meter away.

    I'm a bit surprised to read of the expense of maintaining a 1.5T field without a Pt.

    I'm a bit surprised that the Pt didn't notice the field's effect while the gun was still in his hand.

    I wonder if there was any follow up?

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