Very good article on your problem by Larry A. Willis
Bullet Shape
"The curved shape of a bullet (called the ogive) is more consistent than the actual tip on most bullets. Therefore, you can verify the Overall length (OAL) of your handloads more accurately by measuring back from the ogive to the base. Your chamber pressure and accuracy is affected a great deal more by the positioning of the bullet ogive than by the actual bullet tip. Most experienced reloaders keep this in mind when inspecting their bullets; and when measuring the OAL of their handloads, they measure back from the bullet ogive.
However . . . . there's more to this story. One day while shooting groups, I started getting totally unexplainable flyers. When I examined my handloads, I discovered that they varied in length - considerably. This was a mystery at first, because I made all of my handloads on the same press, using the same seating die, with the same depth setting, and I used the same bullets. So, why did my handloads still measure different lengths when I measured them from their ogive to the base?
That's when I pulled some of my handloads apart and measured the actual bullets. My Digital Headspace Gauge isn't designed for this, but it's also handy tool for comparing bullets. These were identicle 180 gr. match grade bullets, from different lots. I was not surprised to see their length differ by .005" when measuring them to the bullet tip. However, after measuring these bullets from the ogive to base, some of them actually measured .012" different from the others. This shows that it's also possible to get serious variations in bullet shape. Since then, I've seen this happen with other brands of bullets that came from the same box. This inconsistency can be found by comparing individual bullets (or completed handloads) from the ogive back to the base.
I'm sure that by now, someone out there is wondering "Wait a minute . . . . if your bullets are seated from contact at the ogive, how can you find a different OAL when measuring those handloads from the ogive to the base?" The answer surprised me at first, but it's simple. I was taking the final length measurement from a much lower part of the bullet ogive. This shows that the curved shape of a bullet (the ogive) can vary. This lower part of the bullet ogive is much more significant, because it initially contacts the rifling. An inconsistent bullet ogive can also affect the distance that your bullet travels to the rifling. This is an important item to look at when you're trying to shoot tight groups. After that experience, I added another step to my reloading procedure. I now compare my long range match bullets (right out of the box) from the lowest part of the ogive to the base - before loading them.
This tech tip describes how comparing the ogive uniformity can improve the quality of your bullets before reloading. By the way . . . . I've found that if this particular reloading problem is affecting your handloads, this one tech tip can reduce your (5 shot) 100 yard groups by as much as 30%"
Bullet Shape
"The curved shape of a bullet (called the ogive) is more consistent than the actual tip on most bullets. Therefore, you can verify the Overall length (OAL) of your handloads more accurately by measuring back from the ogive to the base. Your chamber pressure and accuracy is affected a great deal more by the positioning of the bullet ogive than by the actual bullet tip. Most experienced reloaders keep this in mind when inspecting their bullets; and when measuring the OAL of their handloads, they measure back from the bullet ogive.
However . . . . there's more to this story. One day while shooting groups, I started getting totally unexplainable flyers. When I examined my handloads, I discovered that they varied in length - considerably. This was a mystery at first, because I made all of my handloads on the same press, using the same seating die, with the same depth setting, and I used the same bullets. So, why did my handloads still measure different lengths when I measured them from their ogive to the base?
That's when I pulled some of my handloads apart and measured the actual bullets. My Digital Headspace Gauge isn't designed for this, but it's also handy tool for comparing bullets. These were identicle 180 gr. match grade bullets, from different lots. I was not surprised to see their length differ by .005" when measuring them to the bullet tip. However, after measuring these bullets from the ogive to base, some of them actually measured .012" different from the others. This shows that it's also possible to get serious variations in bullet shape. Since then, I've seen this happen with other brands of bullets that came from the same box. This inconsistency can be found by comparing individual bullets (or completed handloads) from the ogive back to the base.
I'm sure that by now, someone out there is wondering "Wait a minute . . . . if your bullets are seated from contact at the ogive, how can you find a different OAL when measuring those handloads from the ogive to the base?" The answer surprised me at first, but it's simple. I was taking the final length measurement from a much lower part of the bullet ogive. This shows that the curved shape of a bullet (the ogive) can vary. This lower part of the bullet ogive is much more significant, because it initially contacts the rifling. An inconsistent bullet ogive can also affect the distance that your bullet travels to the rifling. This is an important item to look at when you're trying to shoot tight groups. After that experience, I added another step to my reloading procedure. I now compare my long range match bullets (right out of the box) from the lowest part of the ogive to the base - before loading them.
This tech tip describes how comparing the ogive uniformity can improve the quality of your bullets before reloading. By the way . . . . I've found that if this particular reloading problem is affecting your handloads, this one tech tip can reduce your (5 shot) 100 yard groups by as much as 30%"
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I have measured bullets like that before just for fun to see what the variance is. With Sierra it is + .002. With Hornady it opens up a few more thousandths. 
