Thread by @MichaKobs

A few days ago Bellingcat presented for the first time pictures of a M4000 bomb, which differs considerably in design from the known drawing. The video shows an almost undamaged bomb under the title "One of the unexploded MiGs, thank God".

Reason enough for @ckabusk and me to take a closer look. At first it is noticeable that the well known drawing is stretched for some reason. Instead of the relations 1470 : 460 the shown bomb has a relation of 1784 : 460.

In the corrected ratio of length and diameter the bomb should look like this:

Now Bellingcat showed a Photoshop version of a stocky bomb with big caps, assembled from video stills, but the pictures didn't really fit together (see weld). Nevertheless, they claim that the diameter of those Lataminah and Khan Sheikhoun caps matches the diameter of this bomb.

So with the help of photogrammetry, we rebuilt the bomb from the 2013 video.

If you scale this model to the size of the known caps on Khan Sheikhoun and Lataminah you get a bomb with a diameter of 460mm and a length of 1470mm. However, with this bomb the fins are turned by 45°, the body is shorter and the lugs for the bomb suspension are offset.

Interestingly, in April Forensic Architecture presented pictures of a M4000 with fins turned for 45° and a shorter body. The sudden discovery of the video thus seems to have taken place at least six months ago. At Postol vs. Higgins 2017, the bomb still looked like the drawing.

But now we can assume that those filling caps from Lataminah and Khan Sheikhoun actually originate from such a bomb. And within a few days a second video appeared.

Thr description says:
"Damascus - Tishreen and Hafiriya neighborhood 13/03/2014
Information Office:
One of the unexploded rockets was Assad's planes bombed civilians
In al-Hafiriya area in Tishreen neighborhood, ..."

If one considers the probability of an almost undamaged dud bomb and twice the description that it did not "explode", one can assume that several hundred of them are scattered in the (former) opposition area. Moreover, Assad had apparently told the truth.

But there is more that stands out in this context. This bomb has a heavy steel or concrete casing at its tip. This guarantees a ~vertical impact while the final energy of the 3.5kg TNT acts backwards. How is it possible that the fuse jumped out of the Lataminah crater?

This bomb raises a dozen more questions but it also answers one.
Yes, the "Jihadists" had plenty of wreckage parts of these "sarin" bombs.

One final suggestion for @ForensicArchi: If you re-scale the outer shell then it would make sense to re-scale the inner parts too.

@PhilipWatson_ recently recently published a picture, which according to his article he got from @ForensicArchi. It shows the placement of a crucial piece of wreckage found in Lataminah, but the placement seems wrong.

Two facts speak against this position: first, the ring, which connects the body of the bomb with the tail cone of the bomb, was still connected with that tail cone (that was also found) and it looks clearly different.
And secondly...

...it is questionable what could be attached to this ring. So why the drill holes?
(Note that the mixer arm protrudes beyond this ring.)

It seems much more plausible that this remnant is the middle ring. A similar ring is present in the bulk version of the MYM6000 bomb as well as in the binary version. For all three bombs this ring is only labeled for the bulk version of the MYM6000.

With the help of @amin251 we were able to translate the lettering. The crucial part is الحجاب الحاج and can be tanslated as "interseptum".

So if the bulk version has a ring to which you can attach a partition wall for the binary version, and if the M4000 has also such a ring for the binary version, then it is obvious that the M4000 either existed in both versions or at least was planned that way.

According to the same drawing, it looks as if bolts are holding this partition wall, which is apparently riveted or screwed into the existing holes. (Such a partition must be easily destructible, but it must also be 100% tight to prevent premature reaction. ...

... The wall and the bolts must also withstand the pressure of one component if only one chamber is filled.) So it makes sense to assume that a binary bomb would have steel bolts in those holes. These could either break or be torn out. But then they would damage the holes.

In my opinion, the absence of remains of that partition wall, such as the absence of bolts or damage to the holes, gives me great certainty that it is a bulk version even if a binary version might have existed.

But since this ring was apparently built into these bombs in principle, this ring will also have been present in those 2000 converted HE bombs of 2013 and 2014...

I tried to translate the slides and comments of the Russian MOD regarding the Khan Sheikhoun JIM report. (It's always good to consider both sides of an argument.) ...

slide 4 and 5:

https://twitter.com/CL4Syr/status/1180405252937244673