Lots of good info there, any will give you enough.
The rule of thumb I use is 4 sandwiches to 1 pound of cooked meat. So if I was cooking for 100 sandwiches, I would need 25 lbs of cooked meat or 50 lbs of uncooked meat.
Since this is a self serve event, people will take more than if you had someone handing out the sandwiches so I would up it to around what hamiltont suggested.
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