Jeffrey LewisTerror Farm, Part 2

This is the second in a many part series based on my article with Peter Zimmerman in Foreign Policy entitled “Bomb in the backyard.” For previous posts click on the phrase terror farm .

I wanted to share my favorite moment from writing “Bomb in the Backyard” (aka Terror Farm).

Our scenario, like the novel Gadget calls for the terrorists to refurbish a recoilless rifle to slam the two masses of uranium together (hence “gun-type” device):

To detonate a nuclear bomb, terrorists do not need to fashion the right type of gun. “Team Gun” would likely consist of three or four people, at least one of whom is familiar with the interior ballistics of guns in the appropriate size range. Their principal task would be to find a surplus artillery piece of the correct size and to build a projectile. Such recoilless rifles are widely available in the United States and Canada as military surplus, though they require a license to purchase. A hobbyist could easily refurbish a recoilless rifle for just a few thousand dollars.

We needed, of course, a proof of principle for this statement.

Enter Destiny Densley.

Yes, that is her real name. In fact, that is a picture of her truck, with a refurbished 57 mm recoilless rifle sitting in the back.

She details the whole process in an online forum titled—what else?—My 57mm Recoilless Rifle Project.

A self-described “little old handicapped Lady in Utah,” Ms. Densley also refurbished a 77 mm recoilless rifle and signs her posts: I’m not really into needlepoint or quilting but I can do a nice Grenade Launcher..

Glad she’s on our side.

Apologies for mispelling Densley and misidentifying her occupation in the Beijing version of the post.


  1. yale (History)

    You know where she can park her car…

    Anywhere she wants.——————————————-Uranium guns lend themselves to simplicity and (compared to first generation implosion bombs) small weight and size.

    In an archived ACW comment post (2nd half of last comment in thread) is a very schematic double uranium gun of off-the-shelf-parts

    A terrorist version of the device would likely use more HEU and a steel tamper rather the described mass-optimized beryllium reflector.

    To see where a national (or even sub-national) group could go with uranium guns consider the antique (1957) W-33 gun-assembly artillery shell.Measuring only 0.20 meters wide x 0.94 meters long with an astonishing weight of only 110 Kg!

    It yielded 5-10 kilotons with a 40 kiloton variant (likely DT boosted).

    A couple thousand were made.

    Iran would find it childs-play to build warheads roughly similar and arm its long-range missiles. I cannot imagine Israel standing idly by as Iran ramps up enrichment capabilities.

  2. Allen Thomson (History)

    Back in the early ‘90s I was working in Washington and had occasion to fret about a future in which precision guided mortar rounds would become available to terrorists. “First round into the Oval Office” was the term used to get attention.

    But then a spoil-sport, a former FBI agent who had worked terrorism cases, noted that there were already plenty of opportunities for bad guys using readily available techniques. A truck with a recoilless rifle concealed in back cruising down Constitution Avenue was one illustration.

    My favorite, however, came from noting that the River Entrance to the Pentagon was frequently used by people with hand trucks carrying boxes of documents or computer hardware. The first security check was inside the building—on the floor directly beneath the SecDef’s suite of offices.

  3. Destiny Densley (History)

    My name is actually spelled Destiny Densley and for your information I am NOT an ATF Agent. My little Rifle you have in the photo is Not suitable for fireing a lethal radioactive round… Surely you armchair warriors can find something better to do… Sigh

  4. p32shooter (History)

    well wow

    don’t need a gun – a piece of boiler pipe will do admirably – get a life as the airplane trick can still be used and makes a great dirty bomb without the drama of a real atom bomb


  5. Tim Edgerly (History)

    Where do you guys come up with this stuff???? If you had any idea how hard it really is to get a nuclear device to go off you would see how silly the whole recoilless idea is. If you have real issues post them and maybe you won’t get lumped in with the idiots at the other extreme.

  6. Jeffrey Lewis

    The gun, by the way, isn’t to fire the device but rather to slam one mass of uranium into another.

    A 57 mm gun may be too small for that task as well, but Peter (quite sensibly) didn’t want to do muzzle velocity calculations.

    (Serber’s The Los Alamos Primer, I believe, does get into those kinds of numbers. My copy is at work.)

    We simply used the hobbyist example as a “proof of principle” as to the feasibility of refurbishing a gun.

  7. Jeffrey Lewis

    And who says I am anti-gun? When I lived in Illinois, I was a licensed firearms owner.

    And a terrible shot, by the way.

    Which means if Destiny takes her revenge, I am a dead man.

    Tee hee.

  8. Destiny Densley (History)

    Ah Jeffrey.. don’t worry… I can’t check the 57mm Recoilless Rifle at the Airport… its too Big to fit in a Hard Case per Airline regulations…to haul it to UMD.

    It however does have the ability to bring down a passenger jet on takeoff or landing..

    This weapon is registered as a Destructive Device with the Gov… same Paperwork as a Nuke. It really doesn’t qualify as a “Hobbyist” type of weapon.

  9. Nickolas Jacobs (History)

    I don’t wish to argue for the sake of fighting, but rather for the sake of mutual truth-seeking. Firing two big guns at each other with the idea of having the ammunition collide and then chain react is very (not insulting here) absurd. If one pauses to consider the physics involved, one should arrive at the conclusion that it is also redundant. As a round collapses into any hard target (not flesh) the round collapses and compresses into itself. Similar to a car crumpling about the hood and engine compartment during a crash-test. The particles inside are already being subjected to considerable compression, and yet no one has ever caused a chain-reaction nuclear explosion by propelling masses of radioactive material around into various pieces of terrain.

    A person might try to argue that two lumps of material slamming into each other at high speeds might do the trick, but again, this is absurd. If there is any lateral release of pressure, that is, if either projectile can crumple outwards (simultaneously becoming shorter in length as well as wider in diameter) then the whole process breaks down.

    This is ignoring the complexity of getting two rounds to hit each other in mid-air (on a separate note, I’d love to see to people aiming their guns at each other and firing – the thought IS amusing).

    Finally, LOGICALLY, if it were really so simple, then how come the Manhatten project was so time and resource expensive? All along, they only had to shoot two guns at each other.

    Finally, there have been many reported casing failures of the “relatively” new .40 caliber round, particularly in GLOCKS. The problem seems to stem from the weaker casing compared to the relatively higher working pressures. Talented and professional engineers designed both the GLOCK and the .40 S&W round (indpendently). Even given pedigreed educations, sometimes certain challenges prevent ideal results on the first shot.

    The preceeding exerpt on the .40 and its case failures is paramount to the topic at hand. The idea of using any discarded stove-pipe as a make-shift barrel is an astonishingly ineffective concept. I am not an expert on explosives by anyone’s standard (so take what I’m saying with a grain of salt) – but I do know this. Even without a functioning round to be pushed out of the pipe, simply setting an equivalent of a 57mm “blank” in a stove-pipe will result in one VERY destroyed, peeled back, mangled twist of stovepipe metal. I know this because of some childhood antics and pitifully light explosives in my own makeshift “canon” (and here the round was a tennis ball).

    Nix the stove-pipe, it won’t work.

    Nix the simultaneously fired opposing 57mm canons.

    Nix the reality of depleted rounds somehow chain reacting into nuclear holocaust.

    Speculation is an important step in truth-seeking, but it is NOT a destination. It is irresponsible to treat speculation as fact. Fear as a means of furthering an agenda is terrorism.

  10. Jeffrey Lewis

    Dear Nickolas

    The two rounds are not fired at one another, rather one round is fired at a stationary mass.

    This was the design of the “little boy” nuclear device dropped on Nagasaki.

    Wikipedia has a nice, accessible description of the design.

    For more detailed descriptions, see either Serber’s The Los Alamos Primer or Rhodes’ Making of the Atomic Bomb.

    To be very clear: I’ve said that a 57 mm rr may be too small but that for obvious reasons Peter didn’t want to do muzzle velocity calculations.

  11. Lab Lemming (History)

    Speaking of dirty bombs, any comment on the radiological attack on Alexander Litvinenko? Or is it wiser to wait until Jane is out of Moscow?

  12. Jeffrey Lewis

    Seriously, that thought had crossed my mind.

  13. FIFTYGUY (History)

    As a fellow 57mm Recoilless Rifle shooter, and frequent poster on Ms. Destiny’s site, you no doubt will expect me to have some bias. But bear with me:

    I don’t understand the point about using a recoilless rifle for the trigger device of an improvised atomic weapon. The only advantage a recoilless weapon has over a “conventional” one is system weight under special requirements. By nature, recoilless guns require vastly more powder than conventional guns, EVEN MORE SO THE HIGHER THE DESIRED PROJECTILE VELOCITY. The faster you try to get a projectile launched by a recoilless gun, you either need more powder to keep the system recoilless or you’ll need a stronger (bigger, heavier) gun. Either way, weight/size penalties yield diminishing returns as projectile velocities increase.

    But the only reason that we strive to mitigate the recoil by using a recoilless gun is that by doing so we save on the system weight. This happens by eliminating the need for a recoil absorbing/dampening system (recuperator, buffer, etc.) and the associated structure for mounting and moving the heavy gun (carriage, trail, etc.). For an improvised atomic device, nobody would care about how far the gun barrel recoilled, or whether it stayed pointed in the same direction after each shot, or even if it ripped itself free of its mounting (if any mounting was even necessary). And so we unburden ourselves from the ballistic inefficiencies (and complexity!) of a recoilless design.

    I’m not going to pretend to know a lot about designing an improvised atomic bomb (especially in present company!). Hoever, I would question why a serious attempt would use something even approaching a conventional gun. I would think that explosives would do a better job of propelling the nuclear “bullet”. I understand the importance of a high velocity in such a system to maximize yield. After all, if someone wanted a dirty bomb, simply clapping your hands together might prove suitable, or the same material could be better dispersed with conventional explosives (without an atomic explosion), or easier-to-obtain non-fissile materials could be substituted.

    And I’m sure that there are many, many subtleties to getting a reasonable yield from precious little fissile material. Again, the unnecessary complexities of a recoilless system aren’t justified.

    So please don’t pick on us civilian recreational shooters and our hobbies. We have enough difficulty learning how to get our toys to safely function without having to deal with unfounded hysteria.

    Now, no discussion about nuclear weapons that mentions recoilless rifles is complete without bringing up the Davy Crockett projects. Or, “Weapon System, Battle Group, Lightweight/Heavy M28/M29” as they were rather nebulously known. This goes to show how far paranoia can take you when cost is no object. Just what we needed: thousands of tactical nuclear warheads in the hands of infantry squads on the front lines of the cold war. And only suicidally effective, to only be used in the most hopeless situation. Good thing somebody sobered up and got all those potential “suitcase nukes” taken out of service.

    Now that’s something to be scared of, and it was done en masse by Uncle Sam.

  14. Allen Thomson (History)

    Another point is that gun assembly doesn’t actually require a gun, especially for a terrrorist weapon. If you’re willing to put with a large amount of uncertainty in the yield, assembly velocities in the low double digits of meters per second would do for HEU. We’re talking about strong springs, compressed air and pyrotechnics, not recoilless rifles.


    Adventures of a Physicist;

    Luis Alvarez;

    Basic Books, 1987 ;

    New York, New York ;

    ISBN 0465001157 ;

    EXCERPT from Chapter Seven

    “With modern weapons-grade uranium, the background neutron rate is so low that terrorists, if they had such material, would have a good chance of setting off a high-yield explosion simply by dropping one half of the material onto the other half. Most people seem unaware that if separated U-235 is at hand it’s a trivial job to set off a nuclear explosion, whereas if only plutonium is available, making it explode is the most difficult technical job I know.”

  15. Jeffrey Lewis

    That might be the case, but one of the findings of the study is that there would be no need for a terrorist group to economize.

    A job worth doing, in nuclear terrorism, is a job worth doing well, unfortunately.

  16. Jeffrey Lewis

    Nuclear weapons design is where my credentials are stricly amateur, so let me just point to a couple of paragraphs from the paper Peter and I wrote, keeping in mind that this is what we were allowed to say.

    According to Robert Serber writing in The Los Alamos Primer, even a muzzle velocity as high as 1,000 feet/sec (310 m/sec) is not fast enough to eliminate the possibility of preinitiation of the device if a stray neutron happens to be present after the assembly becomes critical and before it is fully assembled. Thus, there is little benefit to a terrorist group from trying to achieve improbably high projectile velocities.

    A speed of 100 m/s to 200 m/s may be adequate to ensure nuclear yield. A US M40 106 mm recoilless rifle accelerates a six kilogram projectile to a velocity of 500 m/s. All else being equal, by conserving energy it is possible to estimate that the same gun should be able to accelerate an appropriately sized mass to a speed somewhere between 150 and 250 meters per second.

    So, let me amend my earlier comment to say that terrorists will just have to take some risks.

  17. yale (History)

    Dr Jeff wrote:“A US M40 106 mm recoilless rifle …”

    Looks like great minds think alike 😉

    Thats just what I recommended to DD while trying to broker peace .

    As to the problem of predetonation, I will make a S.W.A.G. as to the design spec-ed in the paper (BTW – is the paper available anywhere without subscription?)

    Using 50 kg of 90% HEU and an insertion distance of 0.4 meters from criticallity to full core insertion and a velocity of 200 m/s, then…

    your design would have a rather good 93% chance of full yield. Even a fizzle tho would still be a freakin’ hell-bomb (see NK test).

    By the by, my design uses simple mortar barrels manufactured by the zillions world-wide to achieve 400 m/s assembly (albeit with less reliability due to 2 guns)

  18. Lab Lemming (History)

    My reply got too long and unwieldy, so here’s an exerpt:“Now, I don’t entirely understand the temptation to post recipes for nuclear weapons on the internet- I’ve personally never uploaded instructions for creating anything more dangerous than a chocolate chip cookie.”…and an url:

  19. yale (History)

    Possibly more of a risk than a large unwieldy bomb packed with HEU, is the over-the-counter *Nuke50(tm) MicroNuclear .50 BMG Round* from BWS, Inc.

    BWS has an interesting sales pitch (with a video demo!)

    ==================BWS, Inc. has drawn upon the modern day, virtually untapped knowledge base of post cold war MicroNuclear physics and today’s desire for a compact blast-packing cartridge . Renowned ex-Soviet MicroNuclear physicist “Boris” has recently joined our engineering team to bring the world yet ANOTHER hi-tech BWS product. The perfect addition to your JADED.50(tm) Rifle Kit

    …It’s the Nuke50(tm) MicroNuclear .50 BMG Round!
    (with additional “Concealed Carry” Nuke50(tm) Delivery System also available).

    “Sure, it’s all fun and games …until someone loses a major metropolitan city.”

    What is the Delivery System?

    It happens time and time again. You fire off a M1 incendiary, API Round or even the much ballyhooed Raufoss .50 BMG Round only to be left completely disappointed in the lack of true “Hollywood” blast effects. Many times you just get a poof of smoke …or don’t get anything at all! BWS, Inc has taken a dramatic leap forward in small arms ammunition technology with the advent of the world’s first MicroNuclear .50 BMG projectile. Behold, the Nuke50(tm) MicroNuclear .50 BMG Round!

    Most of you have already heard all of the stories about how the U.S. military used depleted Uranium as the substrate material for the projectiles lobbed at the Iraqis during “Desert Storm”. Now there are all of these quasi-radioactive chunks of metal messing up all of that pretty desert scenery …not to mention the 3/4 million year half-life that many generations must face. Birdman Weapons Systems, Inc. realized the potential of these heavy metal projectiles in combination with today’s modern Celeron/Pentium microcircuitry achievements. We combined these two hi-tech advancements in technology to bring you a mind bending MicroNuclear blast in a tiny, convenient and affordable package. The blast factor of just one single Nuke50(tm) projectile is equivalent to 1.2 tons of TNT! That’s SERIOUS firepower folks! Not only that, you don’t have any chunks of Uranium laying around for someone else to have to clean up!

    Prototype Nuke50(tm) testings (as seen in the video clips) yielded even greater results but were deemed extremely unstable and far too dangerous for the moderately “close range” action found in the Nuke50(tm) Delivery System..

    What is the“Nuke50(tm) Delivery System?”

    The Nuke50(tm) Delivery System is a masterfully designed custom pistol chambered to fire any standard NATO .50 BMG ammunition. The pistol is outfitted with a custom proprietary “BWS Imaging System” for extreme long distance target acquisition with a hand gun. The “complete” Nuke50(tm) Delivery System includes a specially designed “Concealed Carry Case” and a tactical chemical/radiation suit (also seen in the video clips). Although it is not really necessary to have the entire system, it is strongly recommended for persons not properly trained or experienced in current MicroNuclear architectures and related capabilities.

    Note: Although all products manufactured by Birdman Weapons Systems have been thoroughly tested and militarily ruggedized, BWS accepts no responsibility for any death, damage, or appendage loss or collateral damages associated with the use or misuse of its products and services.================================

    Sales Video:

    Live Fire Demo

  20. Jeffrey Lewis

    Hey all.

    I think, maybe, that we should steer a little more clear of the “cookbook” type of advice.

    I don’t think anything here is over the line, but I do think it is right up against it.