What gauge steel are you using for your chamber & how do you roll it [proper gear]. Think i'll crawl back in my hole as You guys are craftsmen [crafts people, better not be sexist in this pc age]. The 10 or so i made over the bucket years were just suzuki quad steel crate base stuff of about 0.7mm, have some wooden cones i spun up to help. 0.8 was a bit hard to roll by hand [long ago, might be wrong] Have tried to roll some cones out of a steel from thinner parts of a stove [& fridge i think] kept it as it measured about 0.7 or 8 but must be high tensile or something as rolled in small flats [might start a new trend!!] Thanks.