Andy,
Unfortunately, you are trying to shoot one of the most inconsistent bullets for bearing surface on the market. Taking a Stoney Point bullet comparator and measuring from the ogive to the base won't cut it.
There are several ways to measure the bearing surface or as close to the bearing surface as we can actually measure. None actually measure just the shank of the bullet. They also get a little of the boat tail in there too. The cheapest and still my favorite is to use two SP comparators (one on each blade of the caliper) and it works great. I marked one of my comparator bodies as "top" and then also marked my second set of inserts as "top". This way I can always be consistent on my measuring.
The second method is the Tubb tool which I believe to be way overpriced and I know to be no better than the SP way.
Using the SP method, I can say that on my last batch of 300 grain MK's, I had .013" variation in measurement. Most of that came from the front half of the shank to the ogive but there were a fair amount that had error in the last half of the shank to the boat tail. Interestingly enough, a few of these latter bullets showed no variation from base to ogive measure! This tells you that there IS inconsistencies in the boat tails of bullets. So it helps to measure from base to ogive but you might miss a few pills that will certainly give you fliers at long range.
As for your concentricity issues, it sounds like you have a real head scratcher.
Ok, I assume you are running the dial on both the fired, unloaded case (and finding straight cases) and the loaded ammo and the problem is truly coming from the loading process. I also assume that you are running a dial indicator on the loaded bullet from the tip to the case mouth, and on the neck of a turned case.
If this is so, then it could be a few things.
The first thing I would try is a bushing die with the correct bushing. The 300 grain MK bullet has a long bearing surface and usually measures .3385 diameter. Neither of these things help when trying to stuff it down a piece of brass that has been squeezed way down by a standard die that gives the brass very much bullet grip. Your expander ball should bring it back to the proper diameter but the brass may have tons of spring back and the die could be taking it down to .243 diameter for all we know.
75% of the time, concentricity issues come about from the dies than any other thing. Brass usually makes up the last 25%. But brass is an easy thing to trouble shoot. Select a piece of brass that runs good concentricity one time and then check it again after firing and reloading it. If it is still good then take a bad one and run the same test. If the good stays good and the bad stays bad, then you have brass issues that your dies probably won't solve.
If you determine it is the dies that are causing it, you will need to determine if it is the sizing die or the seating die. This is easy. Just run the dial over the sized case before seating the bullet. This will tell you what to do next-get a new sizer or a new seater. If it is the seater that is causing it, before you replace it, load a different bullet (preferably a shorter one) and see if the runout is still there. If it is, pitch that die!
If it is the sizer causing it, try a bushing die or a different FL sizer.
I had custom dies made for my 338 thunder (which is on the ultra mag case) and they run less than .001" runout even on my culls. My culls are straight but they were off in weight tolerances.
And yes, it is a good rule of thumb to buy at least one more bag of Remmy brass from the same lot than what you think you need just to have some extra in case you have to cull out a few. /ubbthreads/images/graemlins/wink.gif
Hope this helps.
