I would make it so that the barrels look like they actually go thru the supporting ring of metal. At the moment you can tell that they don't. Think about how you would actually make that thing in real life. Use Booleans to get a simple hole cut in it (I know booleans suck but hey) then scale your barrels a tiny amount so that you get some sort of a lip on it which will look cooler (same goes for the bolts in the legs by the way )

Alan