[dmazur]

Already covered by an earlier post, but I believe it is really hard to set up a resizing die for the correct amount of shoulder "bump" without some kind of gauge.

For bolt action rifles, the chamber can be used as a gauge and bolt-handle effort is the "feedback" that lets you know when you have it right.

With a gas gun, there just isn't an easy way to substitite for a gauge. (Well, you can make a substitute for a Hornady pattern gauge with something that looks like a washer, but then you have to figure out how to use it with calipers and keep everything lined up. Easy if you have lots of experience, but tough if you're just starting to mess around with headspace.)

The LE Wilson pattern is inexpensive, and is a quick check of resizing. Generally, if your resized cases drop to the bottom step, and no further, you should have ammo that chambers easily, yet doesn't have induced excessive headspace (which leads to case head separations.) And it also checks for "trim length" at the other end. And it's fast enough to run every resized case through the thing as a quality control check.

Usually a very, very small adjustment in the resizing die will get you from the top step to the bottom step. (As this can be on the order of 0.006", which is around 1/16 of a turn at 14 tpi, turning the die in another 1/4 turn is usually too much.)