Since then I've been carefully examining videos from the Daraa region looking for more examples of these weapons, and from what I've been able to gather it appears they first began to appear together on January 1st 2013. From about October 2012 one group in that region, the Lajat Armour Brigade, posted videos showing them in possession of RPG-22s (for example here), although not in significant quantities. What appears to happen on January 1st is a number of groups in the region join together to attack the Syrian military in the town of Busr al-Harir, northeast of Daraa city. All the groups involved in the attack appear to be armed with the weapons mentioned above, with only the M60 recoilless gun appearing later than the other 3 weapons, around two weeks into the fighting. During the fighting several tanks and BMPs are destroyed, and from what I can tell the fighters don't seem concerned about preserving the ammunition for these weapons.
While it's difficult to be certain about events my best guess is a large number of these weapons were delivered to one of the larger groups in the Daraa region, which then distributed the weapons to other groups in the region, who all participated in this attack. I believe one of the groups at the center of this may be the Omari Brigade, which appears to be one of the larger and more influential groups in the region, with details of their earlier activities in the region detailed on pages 22-23 of this Institute for the Study of War report.
One other interesting facet of this is that all the groups involved seem to be more on what you could call the FSA end of the Syrian opposition spectrum, as opposed to the Jihadi end of it. This has made me think that perhaps these weapons have been provided specifically to groups that in the long term may oppose the growing power and influence of Jabhat al-Nusra and other Jihadi groups, but currently there's not enough information to come to a firm conclusion.
Since the battle in Busr al-Harir we are now starting to see these weapons appear elsewhere in Syria, for example, here we have the Ababil Horan Brigade, originally based in the Horan region surrounding Daraa, using a M60 recoilless gun in Aqraba, Damascus, the first video of them using this weapon in that area appearing on January 26th
Next in the Hama region we have the Descendants of the Prophet brigade and an Milkor MGL/RBG-6 grenade launcher
And this third video is what I think is the most interesting of all. Filmed in Aleppo it shows a M79 rocket launcher, but what's interesting is who it is being shown to
The man shown in the video is Colonel Abdul-Jabbar Mohammed Aqidi, reportedly the former commander of the Free Syrian Army in the Aleppo province, and now part of the recently formed Supreme Military Council, acting as one of six representatives for the Northern Front, and maybe more tellingly, one of two members of the armament committee for the Northern Front, with this video being one of a series from his recent visit to opposition forces in Aleppo.
So what does this all mean? Well, it's hard to know if it's just a co-incidence that the newly smuggled weapons from the former-Yugoslavia end up being held by a senior member of the opposition in Aleppo, or that they only appear to be going to groups that seem to be aligned with the Syrian Opposition Coalition and Free Syrian Army, but it does seem for certain these weapons are spreading through Syria, and they must be coming into the country in significant quantities.
Youtube playlist - M79 Osa Sightings in Syria
Youtube playlist - M60 Recoilless Gun Sightings in Syria
Youtube playlist - Milkor MGL/RBG-6 Sightings in Syria
Youtube playlist - RPG-22 Sightings in Syria
Unexploded Cluster Bomblets Repurposed As DIY Rocket Warheads
The DIY Weapons Of The Syrian Opposition
Improving Syrian Oppositon Armaments Demonstrated During The Taftanaz Airbase Attack
Clear Evidence Of DIY Barrel Bombs Being Used By The Syrian Air Force
You can contact the author on Twitter @brown_moses or by email at firstname.lastname@example.org