In message .com, crb
writes

Rob Morley wrote:

pounding the rock with the bar should be more effective.

Sorry, it isn't - I tried it!. Kinetic energy considerations?

Farm use is generally for creating fencing post holes in relatively soft
ground. As the sledge is to hand, a few whacks will bypass an
inconvenient flint. Eye protection is rarely worn in these circumstances
so grinding back the mushroom head is a sensible precaution.

regards

--
Tim Lamb