High efficiency barrel stove
This plan requires a 55 gal and a 30 gal barrel, both with removable lids and snap ring closures, and some welding. (You can probably bolt the pieces together, but welding is neater.)
Cut a triangle with 6 inch sides out of the side of the 30 gal barrel, as low on the side as you can cut it. On the non-removable end of the barrel, cut out the opening for the door of the stove. I recommend you use a Vogelzang airtight door kit. Next, you are going to nest the small barrel inside the large one. Then, with the barrels on their side, little one inside the big one, fill the space between them with masonry sand, about halfway up the side of the little barrel. The triangle cut-out should be on top.
At this point, you have a 55 gal barrel on its side with a 30 gal barrel inside it. The 30 gal barrel is sticking out through the lid of the 55 gal barrel, its top almost flush with the top of the big barrel. Inside the big barrel, the small barrel is turned so the triangle hole is upward and unobstructed. The larger barrel is filled at the bottom and halfway up the sides with masonry sand.
Now fit the airtight door to the opening in the small barrel.
Next, line the bottom of the small barrel with firebrick or better, with thinner tiles made of firebrick. This is just to keep the bottom of the barrel from burning out.
Finally, and this is a surprise, cut a hole in the side of the big barrel, near the front of the stove, the door end, and install the stove pipe collar. It should be only a couple of inches back from the barrel end, on the end with the door.
When you fire this baby up, here is what happens. Put in some kind of starter, and pack in your wood. As the fire starts up, leave the draft vents wide open. The vents let air into the front end of the stove and you want the wood to burn from the front to the back. The smoke being generated goes out the triangle hole in the small barrel and the draft pulls it along through the space between the two barrels on top of the stove and to the stove pipe. That is why it is at the same end as the door, not the opposite end.
This makes a really hot stove that has a good thermal mass, operates at a safer heat on the bottom, and has great draft control.