Re: "Non Enemy Troops"
@Voland's right hand - "I cannot be arsed to look it up now, there was a cute photo-essay in the Graunidad showing opposition weapons workshop where they were welding propane gas bottles to the solid fuel rocket engine off a Grad missile.
I suspect that you are mixing these up with "Hell Cannon". They are large high capacity bombs launched from home made mortars. There are loads of "hell cannon" videos on YouTube if you want to see them. The western allied FSA affiliated rebels fire them off in the general direction of "anywhere we don't control", with little idea of what is on the ground where they will land.
The shells seem to be typically made from large propane gas cylinders with fins welded on the back (so the fuse can operate when it lands), but the hell cannon themselves are all different, so there's no specific size or range they have. Accuracy of course is unimportant, since they don't usually have any clue of what is off in that direction other than that it's territory that they don't control. The crude aerodynamics of the shells would preclude accurate targeting anyway. They are sometimes used in the countryside against small villages, but most seem to be used in large cities such as Aleppo, because that's where the groups that use them are concentrated.
As for "barrel bombs" they have been around for decades. I think they got their name because the ones the Israelis used in one of their early wars were made from actual barrels. During the Balkan wars a couple of decades ago, they made them from water heaters. I believe the early Syrian government civil war ones were made from propane cylinders (like hell cannon shells), but the current ones seem to be constructed from scratch in factories. They're just normal (but cheap) bombs in that sense.
The Iraqi government reportedly chucks them all over IS controlled cities in Iraq, but of course that doesn't tick the right foreign policy guidance boxes so the media isn't inclined to report on it much.