I concur with Bart and Walkalong, properly FL sized brass is the best way to achieve consistent accuracy.
As I was attempting to relate in my rather lengthy post, is that about the only time I partial size, is if I'm using brass that didn't come from my rifle that is creating excessive false head space. So what I have done on occasion, is partial size enough to push the shoulders forward, thus eliminating most if not all false head space during that initial fire forming. I do this so I won't experience premature incipient case head separation. Once that brass has been fire formed to my chamber though, I then revert back to FL sizing, thus maintaining a good chamber fit that doesn't exhibit more than .002" of false head space.
But what about new brass, or brass that has already been sized, and is too short head to shoulder, thus exhibiting excessive false head space when chambered? In these instances, partial sizing won't push the shoulders forward, due to the body already being sized, therefore there's no brass to be moved forward. Although there's no real way to solve the excessive false head space issue, well at least short of using an expensive hydraulic brass forming die to push the shoulder forward anyway. But there is at least a way to ensure that the brass will get fully formed on the initial fire forming session. I accomplish this by seating the bullet jammed hard enough into the lands to keep the case head held against the bolt face. Doing this prevents firing pin inertia, and, or extractor button pressure from pushing it away from the bolt face, which results in fully formed brass on the first firing. However, this isn't really something for a new reloader to take on. One must have some experience with their loads / pressures / and rifle before experimenting with this process, or excessive pressures could result.
And even though keeping false head space as minimal as possible is the goal, I don't want it too tight either. I don't like to feel a lot of resistance when the bolt is closed, galling the lugs could then become an issue. So my goal is no more than .002" to .000".
As for neck sizing, when I bought my first neck dies and started into that world, I thought I had found the solve all method for maintaining the dimensional characteristics of fire formed brass. But I soon learned that neck sizing actually introduced other issues. For one thing, and in concurrence with what Bart had stated, at some point the shoulders will have to be bumped back.
Then there is the issue with the body also. Neck only sizing will eventually cause the case body to start binding in the chamber, particularly down near the case head. You can correct that by partial FL sizing, but once again, any time you squeeze the body down, that excess brass has to go some where, which is always going to be up, thus requiring shoulder bump. So thee's really no point, it only creates another problem to address.
So as for exclusively neck sizing, your either going to need a hammer to close the bolt at some point, or the more appropriate, proper method would be to correctly FL size.
There's still times when I neck size, but it's not a die I use all that often any more, and that's because I like my brass to fit properly. One example of when I might neck size only, is if the brass falls out of the chamber with a light tap on the barrel, and shoulders don't need bumping. In those instances, I'll sometimes just run them through a neck die, but usually, they get FL resized.
GS
