several questions

[dspender]

Working on the rudder of my 10 empennage kit
1) Driving 470 rivets in upper rib but inadvertently driving on bare metal of rib and not on rivet. There is an indentation but I see not split metal. Do you try to slowly work out the indentation from the opposite side with gentle hammer strikes backing the reverse side with say a bucking bar or just leave it
2) Driving flush rivets of the skin into the spar flange and the rivet head slides off the machine head and indents the skin where the skin and edge of flange meet. Again no split seen in the metal.
3) Next will set rivets in the trailing edge of rudder. Have used the tank sealant and let it set a couple of days. The plans call for back riveting slowly then turning the rudder over and finish with a mushroom set. Why won't a flush set work instead of a mushroom set?

[Auburntsts]

1. Best probably to leave it as is, lest you make it worse. Try putting some masking tape on the end of the universal set, make sure your pressure is set right, and make sure you're holding the gun as perpendicular to the rivet as possible. The tape will wear out quickly so replace after 4-5 rivets, but it help prevent dings and smileys.
2. Again check your pressure, gun position and that the work is well secured so that you can concentrate on the gun and bucking bar. If your flush set is fixed, you might try a swivel set--it's much more forgiving of less than perfect gun alignment.
3. Mushroom and flush sets are different names for the same thing.