Proper Steel Drum?

Hello,
    I have not seen in posts here or in the Erica and Ernie book what the actual dimensions of the steel drum walls have to be. So, I am to assume that as long as it is a steel drum it is ok to use? I bought a 55 gallon food-grade steel drum and it is definitely not as heavy as most steel drums I have felt. I have had several people including the seller of the drum confirm that it is steel. The seller told me there are different thicknesses of the barrels but it is definitely steel. I just dont want to build this RMH and have the barrel be a weakpoint that ignites because the walls of the drum cant handle the temperatures. I live in Northern California hills and we get freezing temps for short periods overnight. I am building this RMH for my greenhouse and as a 'proof of concept' for a possible house rmh. Thanks for any help in not melting down my greenhouse.  

Hi Ryder; Welcome to Permies!
Any steel drum will work for you.
Preferred, is a barrel with a removable lid. Makes inspection of the riser an easy job
The hottest my barrel top has gotten is 1100 F , has a glowing 8" red circle. Most times it is more like 700-800 F
Average melting point of steel is 2500 F

Thanks Thomas!