You folks that are using just the pot auger and tube into a barrel, how do you have it set up? A new auger and coal tube only allows maybe 1/2 an auger flight to be exposed. Don't especially want to go cutting off a brand new coal tube, esp since likely will build a 'proper' coal bin for next heating season and will need to add the bin auger. But if that's the only way to do it...so be it.
I hate running these with just a pot auger. It really limits the output of the unit since you can't raise the air much past #4 before it starts blowing fumes back into the barrel. A better solution is to get a used bin auger and coupler and extend the pipe a few feed past the auger coupling. If you are determined to not buy any additional parts, you will need to cut the auger tube so 2.5 flights of auger are exposed.