"Plenty lethal" is right. I've heard them called "military loads" because they were popular in the trenches in WWI, for house-clearing in WWII, and close-quarters fights in Vietnam.
When I worked at Zoo Atlanta I wanted to get some for when I stood gun-guard during large animal transfers but the Chief of Security Security Manager said I didn't "need" them. Wasn't her ass on the line if one of the big cats got loose was the real reason. I settled for alternate rounds of 00 buckshot and slugs, and thankfully never had to use 'em.