Kate,
Yes the tube is pretty long to accomodate 9/16 long rivets. The driver does not fit into this tube, it pushes the tube down rather empty or with material between it. If you put a shorter rivet into the tube, lets say a 1/4 long, the driver will push the tube down and still hit the shorter rivet. The tube should push down for enough to be at the same level as the casting. If it doesn't, rust or crud is stopping it.
The wall mount riveter you have is for brake linings.
Bruce,
The older style rivet drivers just rolled the edges of the rivet over like an eyelet. The newer drivers have 6 circular drill marks in them to splash the rivet into 6 splits and roll them over. The reason for this is it takes less presser to "splash the rivet." Weaver's sells the newer replacement drivers for the Rex riveters for around 14 bucks to splash the rivet.