Just did some reading up on 55 gallon drums. Historically, the've had two different thicknesses based on the materials they were intended to hold. Also, there are both carbon steel and stainless steel drums which would offer slightly different resistance to impact, depending on brittleness I suppose. The drum photographed looks to be stainless, but I am not an expert. Still, the drums I used to shoot at were definitely heavy old carbon steel drums that were used for burn barrels and such. I'm fairly certain that over the years, as the economy changed, engineers discovered 55 gallon drums had been over-engineered and could be made lighter and still safely hold their intended liquids. Just as car doors and trunk lids became much thinner over the years too.
