Re: 408 CheyTac die question?
If all brass was created equal, you could possibly get away with neck sizing only.
My experience with the .408 case and the .408 case based wildcats is that if you neck size, you will only get 2-3 firings until you run into an extraction problem. Reason is the amount of pressure you are dealing with. These cases like to push the pressure envelope, and the brass is fair at best. If your load allows 2 thou or less on case expansion repeatedly, you could get away with neck size only. I highly doubt that you'll develope a load with that small amount of expansion.
The reason I full length size these cases, and all my stuff for that matter, is to uniform the outside dimensions of the case. I have found that neck sizing will cause irregularities in the case wall over time and will cause the case to seal differently in the chamber. This will cause different pressures, which will cause different velocities, which we all know is detrimental to accuracy. After all, we are on a quest for extreme accuracy over extreme distance.
The goal is to release that bullet before any part of the case comes in contact with the chamber wall.
I have had great success squeezing brass this way, especially in the .408 based wildcats.