Ned - I asked Hornady if sorting bullets from the same lot would improve the consistency of the base to ogive measurements. Here's their response:
The base to ogive measurement is a more consistent method for comparing bullets than overall length, as the ogive is the most consistent place to measure. Variations in the bullet tips can lead to differences in overall length, but the base to ogive measurement tends to remain more uniform. Sorting bullets by overall length may not necessarily result in more consistent base to ogive measurements within a sorted group, as variations can still occur due to manufacturing processes and material differences. It is recommended to use a bullet comparator to measure from the base to the ogive for more consistent results. If you are experiencing significant variances and it is affecting your accuracy, it may be worth examining the bullets more closely or contacting the manufacturer for further assistance.
My understanding is that the length of the tip is essentially independent of the process that forms the ogive.
What do you think?
For the record, I never stated that sorting bullets by OAL would lead to more consistent BTO measurements. I never said anything like that, so I don't understand why you would be asking Hornady about it. In fact, I don't recall anyone else making such a claim in this thread or in others like it, either. The whole point of my earlier post was quite the opposite. If someone is looking to minimize length variance within the ogive region of the bullet (i.e. between the two critical contact points in the nose region), they're not going to accomplish anything by sorting based on a region that lies outside of those two points; i.e. BTO. The point here is simple: the BTO region lies
outside the nose region. Sorting by BTO will not improve nose length variance, nor is sorting by OAL likely to improve BTO consistency if the majority of bullet length variance lies in the nose region, which it does. In my hands, bullet base-to-ogive measurements are generally far more uniform/consistent than either OAL or nose length measurements, and vary little, if at all. If you want to sort bullets to improve length variance in the nose region, you have to sort them by the length of the nose region, or possibly by OAL as a surrogate for the nose region, but only when the BTO dimension is very uniform. Further, when bullet BTO measurements are very consistent, any variance in OAL measurements must therefore lie mainly in the nose region. This is simple geometry. That is the region where the two critical contact points also lie. Collectively, these observations support the notion that sorting bullets by OAL
that already have consistent BTO dimensions will result in more consistent measurements within a single OAL group between the two critical contact points. Again, this is simple geometry.
My understanding is that the
ogive of the bullet extends from the top of the bearing surface all the way out to the edge of the meplat. In other words, the ogive encompasses the entire curved outer surface of the bullet nose, from the top of the bearing surface to the meplat. That definition is also consistent with the term "ogive radius", or the curve defined by the outer edge of the bullet nose from bearing surface to tip. On numerous occasions, I have lined up bullets from the shortest and longest length groups within a single Lot #, short in front, long in back. It is often possible to observe with the naked eye that the ogive radii of the two bullets are
not the same. If the [centerline] nose length varies between two bullets, by definition their ogive radii should be different, and they are. This observation provides further support for the bullet nose geometry I described above and the effect of sorting bullets by OAL on length variance between the two critical contact points. I seriously doubt someone like Bob Green would make and sell a tool to sort bullets based on the region between the two critical contact points specifically to improve the consistency of seating depth if the bullet geometry didn't support the notion that it would work.
I posted the bullet image above with the critical contact points in order to better illustrate concepts of bullet geometry that occasionally seems difficult to grasp for some. There was no other reason or agenda behind that action. Nonetheless, I would urge anyone not to simply take my statements on an internet shooting forum as gospel or fact. Quite the opposite. I would urge anyone curious about details in the reloading process such as bullet geometry and length sorting to start taking measurements for themselves. Test things, measure things, and then draw your own conclusions from your own observations and recorded data.
