All reloaders end up looking for that magic setting of the resizing die that reworks the brass the least and insures chambering. Somewhere between neck-sizing only and full-length resizing. The headspace gauge insures the round will chamber and not exceed max overall length. The Precision Mic is more accurate, but more expensive. A method (there are many) using the Mic gauge is to "shoulder bump". Just pull the sizer down far enough to bump the shoulder a thousandth or two. BUT, all that is for non-autos and not considered kosher for ARs and the like.
If you can find a setting to use and decrease the amount of work done on the brass and still fully chamber, like Walter is doing, then accuracy usually improves and case life definitely will.
[This message has been edited by sensop (edited April 22, 2000).]