Sorting bullets: Seating Depth vs OAL

[Ccrider]

The best custom bullets vary in OAL. I am seeing as much as .015 variances. This variance in length impacts seating depth and theoretically, how far each bullet goes into the lands. I have two questions. For those of you that sort based bullet length, how do you sort them.

Does the difference in bullet length show up on the target?

 

[Bc'z]

I'm sorting in batches of .003" OAL with all my bullets weather its Lapua scenar or Barts and Eps.
Base to ogive seems to pretty consistent, the variation seems to be coming in from ogive to meplat.
Because the seating stem contacts in this region of the bullet im finding sorting OAL is giving me a more consistent CBTO measurement.
As far as noticing a difference on target.....
I can't hit nothing no way. Lol

 

[Ccrider]

I'm sorting in batches of .003" OAL with all my bullets weather its Lapua scenar or Barts and Eps.
Base to ogive seems to pretty consistent, the variation seems to be coming in from ogive to meplat.
Because the seating stem contacts in this region of the bullet im finding sorting OAL is giving me a more consistent CBTO measurement.
As far as noticing a difference on target.....
I can't hit nothing no way. Lol

How much variation are you seeing in bullet length?

I have been sorting by bullet OAL when I have time. It helps me with keeping seating depth consistent. I am just wondering if OAL matters if seating depth is the same?

If I do not sort, cartridge OAL is different even when seating depth is the same.

 

[Bc'z]

I'm seeing .010" with a few outliers top and bottom leaving me with 3 good groupings of bullets, outliers get used as foulers and sighters.
My CBTO is only showing .0015" variation, I don't worry about overall cartridge length.
My concern is bullets CBTO relationship to the lands.

if you line up 10 bullets and look at the meplats you'll notice variation some being pointy'r more closed, and others more open.
I believe this is where I'm seeing OAL variations.
I'm sure tipping and pointing bullets would help iron out some of the variation.
I suppose a person could do 2 sorts on a batch of bullets, CBTO & OAL.
I don’t have the time or energy to do so as I hate sorting almost as much as trimming brass to length taking bullet pointing off my to do list as well.

 

[RustyInBend]

The best custom bullets vary in OAL. I am seeing as much as .015 variances. This variance in length impacts seating depth and theoretically, how far each bullet goes into the lands. I have two questions. For those of you that sort based bullet length, how do you sort them.

Does the difference in bullet length show up on the target?

I don't sort bullets, but I measure seating in base-to-ogive (using SAC comparators) making OAL irrelevant. I care where the bullet touches the lands, not how far into the barrel the nose of the bullet protrudes beyond the jam point.

 

[JFrank]

Im told by the bullet makers that overall length effects BC of the projectile.

I like base to seating stem.

 

[Chaotik]

I don't sort bullets, but I measure seating in base-to-ogive (using SAC comparators) making OAL irrelevant. I care where the bullet touches the lands, not how far into the barrel the nose of the bullet protrudes beyond the jam point.

So then do you sort your completed rounds by CBTO?

 

[wildcatter]

I could care less about a few thousandths of oal length of my bullet. I do give great concern of my ogive to base measurement, how much bullet is in my case!

How much is out of the case is nice to be exact, but a few thousandths is not my concern, as long as they are seated from base to the top of my neck every time.

I ran into some differences using my Wilson seater as it came with the factory supplied seating stem, seating vld bullets. As the stem bottoms out on the nose of the bullet, this caused a difference because the most difference in OAL on the bullet is the trim of the nose, which some bullet makers don't even do on their bullets after being final formed.

This changes the case capacity, as well as the distance from ogive to lands. I have not found a difference in ogive to base or in the taper of a single bullet made in the same die. The difference has been in how much was trimmed in the final tipping station.

By using the VLD seating stem from Wilson, I went from seating of the nose of these long lean bullets to seating off the side or taper of the bullet, which like the ogive is more consistently perfect bullet to bullet from the same die.

Personally I think if your bullets are good from base to ogive, and you are seating from a properly fit seating stem, designed to fit the sides of the nose and not pushing off the top of the point, you should see no difference in accuracy from slight differences on ogive to point length. I have sorted and tried this and found no difference in my accuracy or velocity.

 

[Straightshooter1]

The best custom bullets vary in OAL. I am seeing as much as .015 variances. This variance in length impacts seating depth and theoretically, how far each bullet goes into the lands. I have two questions. For those of you that sort based bullet length, how do you sort them.

Does the difference in bullet length show up on the target?

I pay very little attention to how far I am from the lands, only to the extent for deciding on a starting point. From there, it's a matter of finding the OCW, then a good seating depth. Consistent seating depth is determined by consistent distance from seating stem contact point to the projectiles base. Because seating depth is most important to me, I sort accordingly, from seating stem contact point to the base in groups with +/- .001". Doing this can give me variance in the typical ogive measurement, then then again, that amount of jump variance that's involved is not important.

Variance in OAL can definitely effect the BC. For long and extreme distance shooting, that can be a big issue. So, also sorting by OAL can be helpful for more consistent BC and for anyone tipping their projectiles too.

 

[dstoenner]

Brian Litz says for long distance sort by OAL. That helps uniform BC for more precision

David

 

[Dusty Stevens]

OAL is the only thing you need if you get good bullets to start with

 

[Ccrider]

OAL is the only thing you need if you get good bullets to start with

How do you group when you sort for OAL?

 

[Dusty Stevens]

How do you group when you sort for OAL?

Group them into similar measurements. Main thing is to catch the outliers

 

[Ccrider]

By way of example, I was sorting custom bullets last night. The OAL varied by .027. Based on that spread, I am wondering whether sorting by .005 would be adequate. With 4 groups, this would catch most of the bullets. @Bc'z sorts by .003. so I did that last night. Was a pia.

 

[rwj]

Anyone trimming bullet meplats to make OAL the same?

 

[Ned Ludd]

Anyone trimming bullet meplats to make OAL the same?

If you're going to sort bullets by OAL to facilitate pointing or increase seating depth consistency, measure OAL before trimming. Otherwise, the way many people set the trimmer using a shorter bullet then trimming all the rest to that length will throw everything off in terms of OAL.

The process of length-sorting bullets by OAL for the purpose of improving seating depth (CBTO) consistency is based on the idea that bullets typically have much greater length variance in the nose region than they do in the boattail or bearing surface. Much of the OAL variance we normally observe within a Lot# of bullets is due to length variance in the nose region. That is not to say there isn't any length variance in the boattail or bearing surface segments, just that the length variance within the nose region is usually much greater. Further, the distance between two critical contact points that determine seating depth, meaning 1) the point where the seating die stem contacts and "pushes" the bullet down into the case, and 2) where the caliper insert seats on the ogive just above the top of the bearing surface when measuring CBTO, is fixed (see attached image below). What that ultimately means is that sorting bullets by OAL is analogous to sorting by nose length, the whole idea being to sort bullets such that the distance between these two critical contact points is very close for all bullets within a single length group. Because the boattail and bearing surface segments fall outside the nose region, sorting bullets by BTO is not going to help with seating depth variance (i.e. CBTO variance) that is caused by bullet nose length variance.

For the OP - I sort bullets by OAL into groups of .0015" total spread within a single length group. But the next group will start at .0005" longer, so there is really .002" between groups. For example, Group 1 might 1.5000" to 1.5015" in length, Group 2 would cover 1.5020" to 1.5035", Group 3 would cover 1.5040" to 1.5055", and so on. I started doing this for the purpose of pointing bullets, but soon appreciated that it also helped make seating depth more consistent without the need for twirling the seating die micrometer by as much as a few thousandths in either direction to ensure that every bullet seated with the same CBTO measurement.

 

[barefooter56]

Anyone trimming bullet meplats to make OAL the same?

You can do this . However you will be affecting the BC NEGATIVLY .

 

[Ccrider]

You can do this . However you will be affecting the BC NEGATIVLY .

Why negatively?

 

[rwj]

Why negatively?

Increased frontal area…

 

[Ccrider]

Increased frontal area…

So the dies do not actually “point”?