"Turn the resizing die down until it just makes contact with the case. ---
Correct if I'm wrong, the shoulder is not pushed back to SAMMI specs by doing it this way. And the cases are formed to the chamber of that specific rifle."
Okay, this is the correction; Case shoulders are NOT formed to the chamber of any rifle that way, not even close. And it may or may not meet SAMMI headspace specs, that can't be said without measuring.
How much, or how firm a contact we make against the shell holder sure affects how much, if any, the shoulder gets pushed back but screwing a die down until it just touches a shell holder means nothing specific. Every press has some spring - deflection - when under pressure, the lever linkages also have some slop, the dies and shell holders have manufactoring tolerances, etc, so no direct "do this and get that" method of die adjustment can accomplish anything. We have to understand what we're doing and adjust for what we want, not follow a procedure.
To adjust a sizer die right you MUST understand that what you probably now think of as a "small" die adjustment is more likely a massive change. Dies have 14 turns to the inch so they move some 72 thou per turn (.0714285" actually). So, changing a shoulder .001" requires a change of just less than 1/72th of a turn, not the often suggested "small" 1/8 or 1/4 turn. In fact, the total headspace range of most bottle neck cartridges is only 6-7 thou and a 1/8 turn equals a change of some 9 thou! By percentage of error, that's MUCH more than the full permissible headspace range and, to do good work, we need to get much closer to a snug fit that that.
Now, from all that, you may understand that we MUST have a gage of some sort to check what we are doing with the die if we really want to do our best work, it's impossible to do so by a formula.
First, we can use the chamber itself as a gage for resizing. Carefully turning the sizer down until the sized case chambers with just a hint of resistance is okay .. but not precise. Much better is the use of one of the various case length "head to shoulder" tools; RCBS' Precision Case Mic, Sinclair or Hornady's LnL gage with a dial caliper or the Innovative Technologies shoulder length tools all work very precisely.