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.