I have had this in the back of my head for awhile. I picked up a 6"x28" 16 gauge sheet of steel. Not having a good way to roll the sheet into a cone I decided to keep the thing square. I layers out the four sides. I cut the sheet in half length wise. Giving me two 18" long by 3"+/- high pieces. From those I cut four sides. 8" at the bottom 5" at the top. Got out my welder and tacked everything together. When I was happy with that I welded the seems.
I won't be able to try it until the weekend. So until then here's the finished shots