What about a drill to remove one of the heads ?then a punch to push them out ?
Almost amazed at the workmanship. Ball peens with a backer and maybe file work after.
Thick steel or iron depending which piece with the rivet swelled to fit and the flush surface on some pieces you can't see the rivet face.
Two were in about 1/4 thick stock and about 5/16th diameter.
I'd need a sponsor for drill bits! And given the size of some rivets they'd be substantial in size.
(I'm imaging smelling hot iron just writing about it.)
This thing has been rebuilt/salvaged repeatedly. But the original beams hardware's are still there. Have to be really.
Found a couple galvanised tees up front yesterday.... Not quite stock.
I used oak mostly when I patched it up decades ago after a neighbor parted ways with it and the home there. And stripped multiple screws from my back then rebuild the other day so I grabbed a drill and squawked a while.
Then got annoyed and used a big hammer instead...









