I live in the heart of what was once The Blackland Prairie which was an ecosystem more completely destroyed by agriculture than Hiroshima was by the A-Bum, and have to say that the post hole digger was designed by idiots for idiots. I’m 60 y.o. with TBI and a salty attitude and will race any 3 teenage boys/girls through 12 post holes using my sharpshooter, also called a drain spade, the Mexicans call it a belduque, rednecks say bill dook, and since it’s long and hard just about everybody calls it a bull d***. 18 inches is stretching the limits of the shooter, but with my Tiger-Crane digging technique I’m certain to win while your boys are scraping black gumbo off their tools and learning how to cuss. True fact of the Blacklands: slaves called it the “hog waller parara.” Look up gilgai for extra merit.
I just set 4 posts in black clay in so cal. I had to add water as I dug and it took me about 1 hour for 4 holes with a post hole digger.