the summer, I was told it will also cool the cob in the summer with enough draw
I'm running 15ish Feet straight 5" black stove pipe then 11ish Feet straight out the roof doubled wall stove pipe, I did not double through the cob
It is in cob imgur link https://imgur.com/a/762If
The Jtube is 5x5 square stock (yes it's metal and before I found permies) with a 12" feed tube x 24" burn chamber x 36" riser in cased in a 10" (I think) pipe with perlite and fire clay insulated, I do have pics of it but not in that imgur link
There are 2 doors wielded on the top and a clean out on the front
But yes the top of the barrel is getting just over 400 and only if I'm feeding it as much as it can burn as quickly as possible. If not and just feeding it every 15 to 20 mins then between 280 and 320.
I did use a laser heat gun to check and it was with 3 to 9 degrees of the one at work so I think its fairly accurate and the one in the pics seemed to be under but fairly close to each other also