Military grade padlocks and the ‘seven parts’ rule…

I do not know if there is any truth to the story, but it is nice to
tell anyway. The story is that guns and rifles never have more then
seven ‘basic parts’. The reason for this is that soldiers will be
confused and make mistakes if the need to clean or repair the gun and
there are more then seven parts.

I hear you think, what does this have to do with locks?

7 parts

Well … besides guns the army also makes use of locks. Locks in
high-security environments. One of the requirements for these locks is
that the core can be replaced ‘in the field’. In case of a missing key,
or suspicion the key is compromised the core of the lock needs to be
replaced asap. Of course they could replace the entire lock, but at
the cost of US$ 1.200 each this is even over the top for the US army.
It is much cheaper to only change the core of the lock.

In order to have people change the core in the field, the locks are
constructed with the ‘maximum of seven parts’ rule in mind.

Han Fey has got some of these real high security padlocks in his
collection. The top model being the Sargent and Greenleaf 833. The
nice thing about this S&G 833 is that it is protected against a wide
range of attacks.

To secure it against manipulation the lock contains a six pin Medeco
Bi-Axial core. Good luck picking or manipulating that …

But what is real special are the ceramic inserts. These strategically
placed strips of hard ceramics prevent cutting and grinding. Last toool
evening by accident a ceramic expert was present. He looked at the
ceramic material and concluded is could probably not even be cut with
diamond drills or grinders. He was impressed by it. Pretty neat.

The S&G 833 is also the only padlock in the world (?) that will resist
an attack with liquid nitrogen. The idea behind this attack is to keep
a lock dipped in liquid nitrogen for 30 minutes, cooling the metal
close to -196 degree Celsius. All other metal objects will shatter if
that cold and hit with a hammer. But not this lock. Supposably the
metal alloy is designed to be secure against this. Unbelievable …

And last but not least all parts of (the military version of) this
lock have a serial number stamped into it. This is to prevent people
‘peeling’ the lock layer by layer until they reached the core. With
the naked core in front of you it is not too difficult to disassemble
it and see the size and rotation angle of the pins. Once an attacker
knows these parameters he makes a key for the lock, rebuilds the core
and inserts it in a fresh padlock. But with codes punched into
different parts of the lock this attack is not made easy.

And last but not least Han shows a military version of an Abloy padlock.

I hope you enjoy another exclusive blackback video on military grade padlocks (10 minutes, WMV 79 Mb)

32 Responses to “Military grade padlocks and the ‘seven parts’ rule…”

  1. Josh Nekrep says:

    There may be truth to the “rule of 7”. I’ve read that all people can manage about 7 unique items in their conscious mind. In fact, it’s been said that is why North American phone numbers (at least local numbers) are 7 digits long.

    Cool lock Barry!


  2. Eric Michaud says:

    $1,200 US (jaw drops) , I’d love to see a link for this padlock for that purchase price, I know in the US I’ve purchased surplus of this exact lock, and I’ve recommended these to a few people where they said they required the best padlock out there, and the only thing that came to mind would be to say well at least the military uses it, but that only travels so far, but they snapped them up to say the least for about $60 US at a military surplus store I know of. I mean at $1,200 US minus unique mountings the Kaba-Mas X-09 is cheaper, and that is one safe dial I am really jonesing for to mess around with and get under a signal processor in a Tempest shielded environment if you know what I’m talking about.(nudge, nudge, wink, wink)

  3. dosman says:

    I noticed Han playing with an 833 in the last video, glad to see more of it now :). The retail price may be around $1300 but the military does get a $1100 discount (see page 7):
    I’ve got some pics and info on the 833’s predecessor, the 831B:

    Cool locks, great video, thanks for the info guys!

  4. Stefan says:

    Nice video with even nicer locks 🙂 Thank you very much!
    I just noticed that the Abus Rock (83/80) doesn’t seem to exist on the Abus website any more – is the big Granit (37/80) its successor? Or ist the 83/80 also only available to government agencies?

  5. DMUX says:

    wow, I need to get a hold of on of our armory locks just like that, I think they cost like 199.98 through supply but I dont know if they could order me one or not

  6. NKT says:

    Argh! Could you put a note that tells anyone without javascript on that they will lose the entire post, or at least still show the verification text if it is off as a reminder?

    Now, as I already said:

    “Haha, I wish I could have played with that at Sneek.

    I’ve seen a breakdown of the location of the inserts, and they seem pretty comprehensive.

    Did your expert guy manage to ID the inserts? They are probably tungsten carbide, but they could be anything, corundum, silicon carbide, boron nitride, or Cubic Boron Nitride (BCN) (about 9.9 mohs). A diamond saw (10 mohs)will get through all of those eventually.

    At that money, however, it could be Borazon, which is 10 mohs, or even just some nice industrial diamonds!

    All the harder stuff is still thin films or not commercially available yet. As far as I know.

    The best trick would be Borazon or diamond rods, or even Heterodiamond coated with a super-hard coating like Ultrahard Fullerite or Aggregated Diamond Nanorods.

    Of course, a good cutting torch would still get you through…

  7. Eric Michaud says:

    I feel really bad hearing everyone paying so much for these padlocks

    They have 3 available.

    But they always get more.

    And of course you can rekey them with pins and such, cutting them with the restricted keys may be an issue, unless you of course have an easy entrie. 😉

    If they won’t send them over seas I think you guys know how to contact me to make arrangements for shipping.

  8. EricM — that’s an S&G 831, not an 833c.

  9. Nick Zakowski says:

    Yes, it is rare to find an 833 for sale. has an 833 example lock that I donated if you want to look at one up close.

  10. Boomboy64 says:

    Gotta love these locks. We have a few of them on an explosives storage locker that were provided to us by the locker’s manufacturer. They’re great, even at -40C. The only detail they forgot to mention was that the keys provided included two different versions. The first week we had it, the foreman used the change key inadvertently and the lock came apart (as it should), spilling all of the (few) pieces into the snowbank. Damn, that was a fun morning…

    Cheers, and keep up the good work,

    Winnipeg, MB, CANADA

  11. Eric Michaud says:

    Ah I finally saw the ceramic inserts quite fascinating, so sorry I made the oops, even though it’s not the 833 but if you do want a cheaper one similar to it the 831c is pretty close. 😉

  12. mark sapir says:

    what is the difference between the 833 & the 831?

  13. NKT says:

    As far as I know, the ceramic inserts are the only difference. There may also be a difference in the metals used for the lock, to meet the cyro-temp requirements, but I doubt it. Anyone know for sure?

  14. Paul says:

    That design of lock has been superceded, the new one is different. The body is made of cast stainless steel I believe.

    I will try to look out some more info on the new lock.

  15. Peter says:

    Hello Barry,

    I enjoy your blog.

    The result you are referring to was published in Miller’s 1956 paper. “The Magical Number Seven, Plus or Minus Two: Some Limits on our Capacity for Processing Information”. An online copy can be found at

    Miller’s paper has been influential outside of the field it originated from in fields as diverse as industrial design, software design, teaching, sales, advertising and presentations, human-computer interaction and even lock design.

    Unfortunately, the premise drawn from the paper is a myth. The above applications are based on a misinterpretation of Miller’s results. The following URL contains numerous rebuttals of the urban myth including one by George Miller himself:

    From Miller himself: “The point was that 7 was a limit for the discrimination of unidimensional stimuli (pitches, loudness, brightness, etc.) and also a limit for immediate recall, neither of which has anything to do with a person’s capacity to comprehend printed text.” (See

    In sum, Miller’s paper is not relevant to any form of design, presentation or pedagogy.

    On the matter of short-term memory capacity, here is a paper that suggests that limit for short-term memory is between 3 and 5 discrete items:

    Regarding human factors and the myth: and

    Regarding technical communication and the myth:

    The popular misinterpration of Miller’s paper has been thoroghly debunked.


  16. novicelockpicker says:

    hey everybody I hope its not too late to post this question but:…where do I get the Abloy PL656 the one shown on the video?

  17. pablo says:

    i have 2 of them if anyone is interested in buying one

  18. Schuyler says:

    pablo –

    if you see this: what price? contact at submit _at_ ndemag _dot_ com

  19. justin says:

    i was wondering if someone would be interested in buying a s&g 833 lock

  20. justin says:

    the lock comes with three keys two of them just open the lock and the other one opens the lock plus opens the internals when turned the other way it has a chain to secure the lock to a structure looking $900 or best offer plus shipping

  21. PFC FOWLER says:

    i need to know the stock number or nsn number for this lock…could someone plz help me out…thanks ..i appreciate it…

  22. Dale says:

    I have both years of the S&G 833 1990 & and the updated 1991 model.

    If someone has a high security padlock for trade I would consider trading 1 or the other for it, please no junk padlocks.

    The 833 padlock is desighned to survive a 7 minute attack while the 831 was 3 minuts of attack.

    The 833 padlock was built because a fella used a rotory hand drill and drilled through the 831 in under 3 minuts.

  23. Gene says:

    I have a S&G 1991 Model 833. Where can you go to sell these things?

  24. Julio says:

    Hi Gene,
    You can sell these on or if you want I might just be up for one, my e-mail is, we can talk about it. Thanks

  25. Mike says:

    Has anyone drilled or cut the ceramic disk in the S&G 833. I am in the process of making an annular cutter rig to take the bottom out.

  26. Erik says:

    Looking for 833s? Drop me a line.

  27. Dale says:

    The 833 retail’s for $1650.00+ as of Oct of 2008

  28. Jon says:

    I have an S&G 833 1991 for sale. only has one key. picked it up during the cleaning some storage lockers. my email if anyone wants to talk about it is your_perfect_sin at the yAH00

  29. Ed says:

    I am looking to purchase an S&G 833 padlock. Please contact me if you have one for sale at I have an S&G 831B-M-1 1988 and would be willing to trade.

  30. rickey says:

    Like to find a blank for the 326c s&d military padlock or know if its rekeyable. purchase one recently on eBay but with only one key.Has no number as the 326c but looks exactly..The key is a medco brand on on one side it says its US military property. Do not Dub.. I need extra key! or try to get it rekeyed..Any luck? Any info? email me at Thanks

  31. Stephen says:

    I have one 833C 1990 Padlock for sale. Comes with the control key. Email me at, if interested.