I have some 660 T-145 steel fence posts on perimeter fence. There are 65 to 75 that are set in solid basaltic lava bedrock. My property is 80 acres. 1320 x 2640.
My neighbor to the immediate south has a commercial jack hammer. He was gracious enough to bore all these holes for me. Before this - these spots had surface mounted posts made out of 2x4's. Kind of a half-assed inverted "T".
He let me try the jack hammer - once. He made the boring operation look easy. It isn't. Main concern - keep the bored hole clear of chips and dust. Otherwise - you end up with a stuck drill bit.
Guys who can run one of these commercial jack hammers - all day long - must have upper body strength like Hercules.