Re: Die setup for .300 Tommy questions..
I try to do like Darryl, FL size only when really needed if things are getting too tight to chamber easily, extraction starts to get a little stiffer than normal with a known safe load. Keeping headspace to a bear minimum helps center the bullet better to the bore, especially if neck clearance is large like most factory always are, still it never hurts.
You can use a Stoney Point Headspace guage on a caliper like I do, it measures off the datum line on the shoulder so you know when the shoulder starts to move back as you very minutely screw the die down lower and lower. If you don't move the die down about a 1/32nd to a 1/16th turn at a time checking all the way for signs of movement, the shoulder will bump back alot real quick, often exceeding .005-.007" shoulder setback in one little adjustment! That's way more than's needed too.
Check your "average" group sizes over several groups when FL sizing verses just NK sizing them, you'll find the FL sizing opens them up noticably more than likely. My Ultra went from just over .5 moa to a solid .9 moa with just FL sizing. Not a conclusive test yet but, not one group went better than .8 moa. Compare that to some that were all the way down in the .3's and .4's.
Something else to consider when FL sizing is when the shoulder is bumped back, it will often bulge the case just below the shoulder and you'll need to go further if it does just to bring it back in enough to chamber smoothly. This will be noticed escpecially whn you get close to bumping the shoulder back as you try to chamber the case while progressing moe and more. The case will get increasingly more difficult to chamber and then finally it will get real easy all at once. The shoulder may have been moved back plenty far, just that the body of the die is not small enough to control the body dia until the case is up in it damn near all the way. The body being sized down will first move the shoulder forward causing most of the tightness closing the bolt when you start moving the die down to get it set up. Monitoring the datum point length will tell you where the tightness is coming from along the way as you are setting the die up.
If you are bumping the shoulder and sizing the neck at the same time, I'm assuming you don't have a neck die for it and just want to "Partial FL Size" them. Screwing the die down just far enough to move the datum point on the shoulder back a couple thou should get you there.
One more thing, If you don't have a headspace guage of some sort yet, just find a piece of pipe, tube or something like that fits over the neck and is flat and square on both ends with a hole in it the diameter that about equals the diameter of the middle of the shoulder on the case in question. Slip this onto the shoulder and use a dial caliper to measure the base to the top of the pipe or whatever you're using to indicate off the shoulders datum line to monitor any bump in the shoulder when you are sizing. You could make a fixture to hold a washer you could slip into or onto it and you're in buisness for a number of inside diameters you can drill the washers out to.