My electro barrel was a closed head with 2 bung holes with caps.
Closed (tight head) barrels tend to be narrower at the top and bottom than in the middle.
I used my Milwaulkee Hackzall to chop off the top. These barrels I can obtain locally for $12 ea. (price has probably risen a bit in 2 years though).
Good thing I bought two, because the first one I cut was about 3/4 inch too low, and would not hold it's shape. The top rim was much thicker than the body,,,,, lesson learned the hard way! ::)
Open head, straight sided HDPE barrels which are reclosable as Jeff states above, are more difficult to find in my area. I have located a place that sells them in various sizes, but it is going to be a bit of a trip with the F150 to go get them.... hopefully spring, I'll get my derriere in gear and go get them! :) The new barrels will be my lye baths, so I can stop worrying about cracks and potential leaks......... :P