I'd also like to point out - all these runout numbers people throw out don't mean much unless you know where on the cartridge or bullet it was measured. Taking a measurement near the case neck is a lot different than at the tip of the bullet. And if you measure near the tip of the bullet, it makes a big difference if you're loading something short like an 85gr SPT, vs a long bullet like a 105gr VLD; the longer distance from the case neck to the bullet tip can result in larger apparent runout value than a short bullet with runout at the same angle.
Or, there are runout gauges that balance the cartridge base and bullet tip, and measure runout near or on the case neck; that gives a very different runout value.
So with that, where are you guys measuring runout, and how are you keeping the measurement consistent and comparable?
I've been taking my measurements just behind the ogive. If you asked me, "Why there?"; I'd answer that I had to pick some place on the bullet, and after having already given consideration to the issues you raised regarding the length of various bullets, it seemed a reasonable answer, even though I know it still isn't a perfect answer. As far as I can tell, and I'm early into this, so long as I take the runout measurement from the SAME PLACE on every LIKE KIND bullet after it's seated into the case, I can
make use of the data derived. By contrast if I'm taking measurements from different locations on the same bullet, across a string of 5 cartridges...well then that's trash data. Completely useless. I suspect one could have range data taken from the tip of a bullet, say a range from .003-.006, or range data from just behind the ogive, say .0012-.0035, and you'd still have useful data in both cases. It should be noted that this method slaves me to the load testing of a single bullet brand and weight for however many strings of loaded cartridges I make, because once I set the measure point on my gauge, I cannot move anything on the gauge, and then expect to return to the previous point of measure on the bullet. I think this works in my favor because the cartridge indexes into my gauge in the exact same place every time. I tested it and it's perfectly repeatable. The seated position of the case does a good job of revealing runout either in the neck (if you are so inclined to measure it), and even more so when taken from behind the ogive on the loaded cartridge. In fact that principle is the same you mention above, relatively speaking.
I think the key to keeping your measurement consistent so that it is in fact comparable (useful), you need a gauge that allows you to index your case in the 'holder', the same exact place every time, and it needs to stay there as you rotate the case to take the measurement. That your data is useful is in my view, more important than the differences between things like nose to case head, or neck opening to case head, etc. I think you are correct that you will in fact get different data from those different methods. The thing I do NOT know is which is more useful when shooting targets or game under 200 yards. In fact, I'm skeptical that one method of deriving runout data (meaning where you take your measurements from and where you index the case itself) is superior to another method used on the same cartridge. I'm excluding the idea of taking runout measurements from the neck of the cartridge AFTER the bullet has been seated. Mostly because taking the measurement from a repeatable index point on the seated bullet seems more intuitive, especially since seating a bullet has a tendency to exacerbate neck runout measurements. Again - the context here is target work and game taking under 200 yards.
