Back to Bullet base to ogive

I proceeded to measure 100 bullets from the base-to-ogive (BTO) and they ended up in 11 groups ranging from 0.588 to 0.574 inches. The difference suggested to me that if I seated the 0.588 bullet 0.02” from the rifling (leade), the longer 0.574 bullet would end up 0.014” further away, or 0.034” from the rifling if I seated it at the same die setting.
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I did not read every post in this thread so apologies where applicable if I am repeating something that has already been pointed out

bullet base to ogive will only affect the case volume of a completed round, not the base to ogive. The base to ogive is indexed off of only two points of contact. The cartridge head sitting on the case holder and the stem of the seating die.

Depending on the cone shape and depth in the seating die stem it is possible that the stem is contacting the meplat not the ogive of the bullet thus resulting in different cartridge depth to ogive measurements. A quick way to check this is measure the overall depth of several cartridges and if the base to meplat is the same on all yet the base to ogive is different you have isolated the issue
 
Std7mag, to answer your question, somewhere along the line I bought a Remington cleaning rod that was accompanied by a plastic muzzle crown protector, best described as a “V”-such that when the rod is passed through it at the muzzle a flat surface is available to rest the tip of a “Sharpie” ultra fine point “magic marker” pen at a 90-degree angle to the rod.

As best I can measure with a micrometer for this discussion, the thickness of the “Sharpie” line is 0.0328” or 0.833mm. As mentioned by Unclenick, the distance between two adjacent lines can be measured with a magnifier and a micrometer using the bottom of one and the top of the other line. That becomes convenient if the full circle I mentioned does not incorporate the initial half-circle. That measurement allows me to adjust the seating die until subsequent circles produce a single circle where the initial half-circle was.

I’m sorry if you find this “messed up, screwball ways to get no meaningful information” but I’ve used it over my 45 years of handloading 14 calibers of 26 rifles to determine the desired jump to the rifling. In only 3 of those rifles was I unable to produce a load that gave 1-inch or less groups.

Unclenick, once again let me thank you for your valuable experience and advice. I will put it to good use.
 
:::chukles:::: and people still cannot grasp why you could seat a .243 105 gn bullet and a .243 68 gn bullet without changing the setting on the seating die and the case head to ogive measurement would not change. Assuming that the profile slope of the ogive from bearing surface to meplat is the same. The length of the bullet is completely irrelevant

spatial relationships are hard for most, less than 10% of the population can solve rubiks cube
 
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