Steel Fence Posts - Drive or Set in Concrete?

[/pine]

There is no (natural) lift on fence posts...all the forces are lateral...
IMO, the least undisturbed material around the base of the post will prevent the least movement.
FWIW...
A neighbor in FL (where the ground is very sandy) was a fencing contractor...mostly wood privacy and chain link enclosures were his mainstay...he always said it was a waste of time mixing concrete to set posts...he said gravel and sand (crusher run etc.) compacted in layers with a sawed off shovel handle etc. worked well...he said if you were going to buy sackrete like bags to not bother mixing it just pour the dry mix in and pack it in around the post as it was poured...

 

[gsganzer]

I've built about 1200' of 2 3/8" pipe fence at my house with top rail and mid-rail. The pipe comes in 32' lengths, so I cut (4) 8' poles from each length. I don't own a pounder, so I drill and concrete them, with them set from 2'- 3' deep. Because I did a mid rail, I set the posts at 10' apart (I end up with less than 2' of waste from each stick of pipe when I cut the midrails. If your using new 2 3/8" pipe, chances are it will actually be structural tubing with a 0.140" wall thickness. (Actual ASME rated pipe is typically too expensive for fencing). This thinner wall can be a proplem when you weld your toprail, because the heat will deflect it ever so slightly at each weld at the posts. You'll get a slight wave on the top rail. For me, I could live with it. Another option is to use actual drill pipe for the top rail and it will deflect less.

If I had a pounder, I'd pound them. That's what all the fencing contractors do. It's simpler, quicker and they hold better. Make sure you have a good torch with a large rosebud. If one of your poles gets askew, you can heat it at the base and bend it to get it straight.