In July 2001, an officer <snip> had an incident where his issue firearm
malfunctioned. The Smith & Wesson, Model 4013, .40 S&W caliber,
semi-automatic pistol was found to have a magnetized firing pin, which
stuck to the side of the channel within the slide. Upon inspection, it was
determined that the entire pistol had become so magnetized that paper clips
actually stuck to any metal surface. The department armorer was able to
demagnetize the firearm with the use of a high-power, videotape-erasing
unit after complete disassembly. When the malfunction was discovered, the
officer had no idea of when or how his pistol had become magnetized. A
review of the officer's activities, revealed that he had investigated a
burglar alarm call at a medical office that was equipped with a Magnetic
Resonance Imaging (MRI) unit. During the investigation, the officer had
walked into the MRI suite that magnetized the pistol. MRI medical personnel
indicate the magnet is always on so they have detailed instructions on
safety, which include keeping metal objects away from the unit. Upon
further inspection, two additional officer's firearms were also found to
have been magnetized.
RECOMMENDATION
ALL ISSUE FIREARMS SHOULD BE CHECKED FOR THIS CONDITION
Police department and medical facility security administrative personnel
should notify officers of the following:
NEVER ENTER AN MRI SUITE IF YOU HAVE ANY METAL OR ELECTRONIC DEVICE
IMPLANTED IN YOUR BODY
Investigations within medical facilities could magnetize an issue firearm
rendering it inoperable.
The test to determine if a firearm has become magnetized is to place a
paper clip next to the firearm.
If the paper clip sticks to the firearm, a supervisor should be notified
immediately.
A trained department-designated officer should verify the firearm is
magnetized and the firearm should be demagnetized with the use of a
high-powered videotape-erasing unit after it has been completely disassembled.
The firearm should be test fired prior to being returned to service.
The fact that there is no outward sign that a firearm may not function as a
result of MRI/magnetic exposure makes this problem difficult to detect.
Awareness of this situation may prevent serious or deadly consequences.

you can get an actual demagnetizer from any machine shop tool supplyer,they're common in the surface grinder dept's

What's the "FBI list"?

MRI magnets are very strong. At a local hospital recently, a little boy was killed when an oxygen canister flew into the MRI machine and hit him in the head. I imagine if the officer would have had his gun drawn, it could have been pulled right out of his hand into the machine.

MRI magnets have VERY strong fields.I maintain and repair them.

There are plenty of stories about some dipwad, bringing metal in a scan room.

To demonstrate to the "Youth-for-Medicine" students, I take a 12 inch cresent wrench and tie a nylon rope to it. Then hand the wrench to a student and have them approach the magnet opening, it always, flies out of their hand. I then have each student try pullin the wrench back from the magnet, which can be very difficult. Hopefully, this leaves impressed on them, the power of the magnetic field that is present.

thanks for the post. i have a Clystron magnet from a $200,000 piece of equipment used by NASA
i use it with a strong rope to recover metal objects incuding boat anchers in the gulf of mexico. i keep it in the barn. it has screwed up a few TV sets already!