I have a ton of '06 brass, lots of spare time, and a local shortage of inexpensive .308 brass
http://www.saami.org/PubResources/CC_Drawings/Rifle/308%20Winchester.pdf
http://www.saami.org/PubResources/CC_Drawings/Rifle/30-06%20Springfield.pdf
Me to? No, not for the same reason. I have purchased 30/06 cases for .01 cent each, $14.00 worth. I have purchased 30/06 linked ammo in three belts for $7.00 each belt. I have purchased thousands of new match pull down cases from Pat's reloading in Ohio for $70.00 a thousand.
"Spare time" I form cases. I form Japanese 7.7mm58, 8mm57, 7mm57 30/06, 8mm06 etc., etc.. Not for all the same reasons, for different reasons the cases like the 308 W are too short. I form cases, I am not a fire former, I do not chamber a round, pull the trigger just to see what will happen.
The 30/06 shoulder is .379" ahead of the 308W shoulder. When forming 308 W cases from 30/06 cases I determine the length of the 308 W case from the shoulder of the case to the head of the case. I choose to add .010" to the length of the case from the shoulder to the head of the case. If after forming the case I can attempt to chamber the formed case if the formed case does not chamber I can reduce the length of the case by lowering the die a pre-determined amount, something like .005". and try again, with control I can form the case to fit the chamber from the shoulder of the chamber to the bolt face.
After forming the case it is a matter of if measuring the length of the case from the datum to the case head to determine the length of the chamber from the datum/shoulder to the bolt face. Some choose to purchase head space gages, that would be 3 gages from go, to no to beyond. A case former that understands the methods and or techniques of case forming can form 11 different case length from minimum length to field reject, and for the Mauser 318 and 323 30/06 cases can be formed to minimum length to infinity.
7.62 NATO and 308 W. The 7.62 NATO chamber is generous at the neck, it is always good to check but reducing the neck diameter is not necessary. When forming 30/06 to 308 W check the outside diameter of the neck. I have tightened the neck of 308 W chambers by forming 30/06 match cases by .006", with standard 308 W cases the neck of the 308 W case expanded .014", only because I was asked to. Seems the bench rest rifle was said to have large chamber necks. Problem, the rifles shot one hole groups, the owner/shooter read on the Internet the necks had to be snug if not tight? It was my job to tighten the necks, after forming the cases the neck expanded .004", and still the rifle shot one hole groups.
Forming dies, if I had one forming die it would be the 308 W trim/forming die, if I had two the other would be the 2243 W trim/forming die because it is short. The short forming die can be used to form the 7.7 Japanese, 8mm57, 7mm57, 257 Roberts etc. if the reloader doing the forming understands the die and press have threads, and they have to have confidence in their ability adjust the die off the shell holder with a feeler gage.
What is a case former to do when the problem is the 30/06 chamber. I purchase cases from shooting ranges that have been fired in trashy old chambers, chambers that are too long from the shoulder to the bolt face. All I have to do is start forming the long case to fit my chamber by controlling the gap between the bottom of the die and top of the shell holder. That would be for all chambers except for one chamber. I have an Eddystone M1917 with a chamber that is .016" longer than a minimum length case, I add .014" to the length of the case from the shoulder to the head of the case. By adding the extra .014" to the length of the case from the shoulder to the head of the case I have .002" clearance when chambering the rounds.
The 280 Remington case body is longer than the 30/06 case body by .051", meaning when determining the length of a 30/06 chamber from the shoulder to the bolt face a case forming rleoader can start forming the 280 Remington case by screwing the die down in small increments after that have initially formed the new shoulder back .041". Notice I did not say 'bump' I can not bump, the shoulder on the 280 Remington case does not move, part of the body becomes part of the shoulder, part of the shoulder becomes part of the neck again, the shoulder does not move, if the shoulder was bumped/moved the case body would have to expand, compress.
F. Guffey
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I like eating donuts BUT if you use 30-06 cases to make .308 cases you will end up with donuts you can't eat. 
