In the last year Syria has escalated its use of barrel bombs by introducing larger “container bombs”. This employ whatever large metal container the Syrians can find and with these Syria had improvised bombs about three times as large as the barrel bombs. Thus barrel bombs now range in size from 200 kg (440 pounds) to a ton. Despite receiving more ammunition from Russia and Iran since 2011 Syria began running out of aerial bombs by late 2011 and resorted to improvisations. Thus Syrian helicopters were soon seen dropping barrels filled with flammable liquids and explosives, rigged to explode when they hit the ground. Syria denied it at first but some of the men operating those helicopter bombers could not resist the temptation to take videos (with their cell phones) and post them.
This sort of weapon is not unique to Syria and has been seen for years in Sudan where the government uses “barrel bombs” rolled out of transports and helicopters. These are not precision weapons, but if the target is a village or other residential area, they are accurate enough. Since 2012 Syria has dropped over 5,000 barrel and container bombs, mainly on residential areas where pro-rebel civilians are living. Syria does not publicize its use of barrel bombs nor does it admit to deliberately targeting civilians. While these barrel bomb attacks have killed over 10,000 civilians, the main purpose of the weapon is to force pro-rebel civilians to flee the country, which several million have done.
Moreover, using improvised bombs means there is no need for trying to find someone willing to sell you aircraft bombs. That may not be practical because of international arms embargoes. Both Syria and Sudan are under such embargoes. The barrel bombs are easy to build locally from components that are legal to import or fabricate locally. On the down side Syria has worn out most of the helicopter and fixed win transports because of all the time in the air hauling and dropping these improvised bombs.