I have tried to drive in metal fence posts and never get more than three inches in before hitting rocks. Sledge hammering doesn't accomplish much. The last time I needed to sink some 4x4's the hole ended up 3 feet across, after accounting for the rocks in the way.
Any tricks to getting thin metal posts in?
I'd rather dig a 100' trench in Florida than a 10' trench in N Georgia. When we had a friend with a backhoe dig this septic field for us (about 60' long IIRC) I don't think we found ONE rock!
Rock sure make a difference. (preaching to the choir here, I'm sure)