Only partially equipment, mostly self-induced (on my part).
My third rifle (first was a Glenfield Model 60, second was a Colt AR) about 32 years ago. Remington 700BDL in 30-06, bought used.
I figured that a rifle of that power deserved a scope, so I bought a Bushnell or something of that ilk. Then a set of "See-Through" rings. See where this is going? I sure didn't...
I "bore-sighted" it by removing the bolt, setting the rifle on sandbags, looking at something 100 yards away through the barrel and then looking through the scope...and adjusting the scope to align with the barrel.
Hey, don't laugh...it actually works.
Took it to the range, and I'm chasing it all over the paper...what??? Finally realize that the scope is turning in the rings. I don't have the right Allen wrenches, so I'll just look under the scope and see if I can't get a decent group using the iron sights...gotta love those see-through rings, eh?
Now do you see where this is going? I still didn't...
Anyway, I snuggled in on those iron sights, lined up on the target, and caressed that trigger...BAM!
Seeing stars...and bleeding from a crescent shaped gash just above my right eye. Now I know what a good punch from Manny Pacquiao feels like.
I learned a few valuable lessons that day...