A recent media video following a platoon of the Syrian Arab Army take over of al-Bukamal, a city in the eastern portion of Syria, on the border with Iraq shows a soldier with what appears to be the receiver, trigger guard, and stock of a shotgun (Remington 870 from the open source photographs) combined with what appears to be a four foot long pipe attached to it. Unfortunately, our only perspective of the weapon is from behind the soldier carrying it, which obscures the receiver, what would most likely be the pump action charger and the ejection port.
Our best guess is that this weapon is a counter UAV device. Essentially it is a shotgun that has been married to a large diameter pipe and uses 12 gauge shotgun shells to propel a larger munition, such as a pyrotechnic, UAV catching net, or another round of some sort to take down a UAV. If you look closely, you will notice that the soldier still has his AK74 (or similar AK Century series rifle) primary rifle, but is equipped with this device on a platoon or company level. Evidenced by subsequent screenshots, the same member of the platoon is throughout the entire video among the Syrian troops assaulting the city.
There is a program within the U.S. Air Force to use shotguns to take down UAVs.
Just as interesting is the use of numbered compounds by the Syrian Arab Army. This technique was used extensively by mapmakers in Afghanistan as a way to accurately identify specific compounds by troops on the ground.