Base to Ogive variations

[Keith Glasscock]

I have never seen so much variation in a box of bullets. I need some opinions about how much is too much.

After measuring 100 bullets, I have the following:

(all based off the shortest bullet)

.000 = 1
.001 = 8
.002 = 16
.003 = 14
.004 = 45
.005 = 13
.006 = 3

So, I have an ES of .006" and I only have one group that would be of adequate number ot shoot a string of F-class. Of course, I have not yet weight sorted the bullets.

So here is my question for the long-range shooters:

Should I open the other several boxes and combine groups? Are these just too varied (should I send them back)? Has anyone experimented with base to ogive in order to tell how the variation will affect performance?

Thanks,
Keith

P.S. I'm headed out to weigh them. Will update.

 

[Keith Glasscock]

I also weighed the 45 bullets in one group.

There were 6 that were -0.1 grains, 2 that were +0.1 grains, 1 at +0.2 grains, and the rest were dead on.

ES = 0.3 grains

 

[areaone]

I measured some 120 gr Sierra 6.5, consistently inconsistent. .0014 spread.

 

[Joe O]

When a friend told me he had large variation on Sierra Match Kings for his 280,I came home and measured my Sierra 95 gr 6mm Match kings.The first two bullets were .015 difference,and they were all over,with about 40 out of the 75 I had,falling into a consistant range.That's unaccptable.Serra's answer ,was to sort the bullets?????.My friend switched to Noslers and everyone out of the box was right on.

 

[Leaddog]

I would shoot the 45 as two strings and the 16 and 14 as another. Unless you are loading to just kiss the lands, you aren't going to see any difference. Use the remainder for practice.

 

[johnmyers]

My last experience with 6mm 107 Sierras is very good. I measure boat tail to ogive and from a box of 500 90% of them are within a .002 range and the other 10% is only .001 on either side. They also shoot well. Charlie Watson was right on with his post.

 

[timeout]

In my limited experience, I found 69 gr. HPBT's Sierra Matchkings for .22 cal varied all over the board. These were the first I had ever ran through the comparator process and I was thinking that my method of measuring was faulty. I next tried Bart Ultras and then Berger VLD's. They were almost spot on, with very few exceptions and then only plus or minus .002" at the worst. I did find a variation between lots on Berger of .005", but within the different lot it was still consistent. I don't like to knock a particular brand or product, but Match Kings don't meet my standards. At least the ones I had don't. Your results may be better and I hope they are.

 

[gatorman]

with human error..you will never know which ones you shot unless you have them all marked.

I stopped that sillyness about weighting bullets and primers as well as cases long ago
to me it is and was a waste of time....All bullets are like that..You will find even some
Bergers as well..So stop wasteing your time and get to shootin...

 

[Keith Glasscock]

with human error..you will never know which ones you shot unless you have them all marked.

I stopped that sillyness about weighting bullets and primers as well as cases long ago
to me it is and was a waste of time....All bullets are like that..You will find even some
Bergers as well..So stop wasteing your time and get to shootin...

What discipline and range are you shooting? I'm curious because I'm seeing most, if not all, of the competitive shooters in F-class doing some serious sorting for long range.

These bullets are for long range exclusively. I want the rifle to hold waterline in a way that'll make your eyes water. I can't imagine that a variation this big in bullets won't have an effect, instead I'm asking for the experience of others as to what I can get away with.

I agree that there is little purpose in sorting for mid-range - maybe a little difference at 600 yards, but at 300, you couldn't tell the difference in my experience.

 

[Alex Wheeler]

Do a quick test, load 5 all the same and 5 with the largest spread and shoot em. Then do it again. Then report. I usually sort to batches of .002''. But most the time I don't have the time to sort and shoot em right out of the box. But if the bullet I shot were as bad as those, I'd find time to sort. I shoot br not f-class. I don't think I'd bother in f-class. Doesn't seem as critical. But I may be wrong.

 

[Keith Glasscock]

Do a quick test, load 5 all the same and 5 with the largest spread and shoot em. Then do it again. Then report. I usually sort to batches of .002''. But most the time I don't have the time to sort and shoot em right out of the box. But if the bullet I shot were as bad as those, I'd find time to sort. I shoot br not f-class. I don't think I'd bother in f-class. Doesn't seem as critical. But I may be wrong.

Therein lies the rub, I don't have access to a 1K range except during matches. I've run a variety of tests at 600 only to find that they are very difficult to extrapolate to 1k.

I think that long range BR and F-class might be more closely related than you think. We are all trying to shoot a 5" or less group perfectly centered in the target. BR just does it blind, and we have the disadvantage of having a variable delay between shots.

I know that I recently had a lot of bullets that came out .025" shorter than the previous lot. It threw my tune completely out the window. This lot is .012" longer than those. I'm thinking I'm gonna have to retune again...

 

[memilanuk]

Interesting... I recently started sorting by base-to-ogive; previously sorted primarily on bearing surface.

Either way the bullets I've been sorting have been very consistent, apparently.

Majority (say 50%) @ 0.000", then probably 30-35% @ -0.001, 15-20% @ +0.001... with a few (probably 1-2%) hitting +0.002"

I've been kind of wondering if I'm really going to see any meaningful difference down range for the effort expended, given the relatively tight spread as compared to some of the other numbers I'm hearing.

That said... one person I've talked to who has done a lot of sorting - and testing, with occasional access to Doppler-equipped ranges from what I gather - said that he'd shot rounds with bullets having bearing surfaces that varied by as much as 0.030", and the actual change in BC was fairly low... as in low enough to just about be lost in the noise, in statistical terms.

I know we're all looking for 'perfect', or at least 'better', as compared to straight out of the box... but sometimes I wonder if its really worth it. Like Keith, I've tried testing some variables @ 600yds with results that go one way one time and the other way the next. Actual 1000yd range time is fairly limited for me.

Monte

 

[6BRinNZ]

Interesting... I recently started sorting by base-to-ogive; previously sorted primarily on bearing surface.

Either way the bullets I've been sorting have been very consistent, apparently.

Majority (say 50%) @ 0.000", then probably 30-35% @ -0.001, 15-20% @ +0.001... with a few (probably 1-2%) hitting +0.002"

I've been kind of wondering if I'm really going to see any meaningful difference down range for the effort expended, given the relatively tight spread as compared to some of the other numbers I'm hearing.

That said... one person I've talked to who has done a lot of sorting - and testing, with occasional access to Doppler-equipped ranges from what I gather - said that he'd shot rounds with bullets having bearing surfaces that varied by as much as 0.030", and the actual change in BC was fairly low... as in low enough to just about be lost in the noise, in statistical terms.

I know we're all looking for 'perfect', or at least 'better', as compared to straight out of the box... but sometimes I wonder if its really worth it. Like Keith, I've tried testing some variables @ 600yds with results that go one way one time and the other way the next. Actual 1000yd range time is fairly limited for me.

Monte

Arguably not surprising - this from the Berger web site

How Sectional Density and Form Factor comprise BC

In words, the Ballistic Coefficient of a bullet is it’s sectional density divided by its form factor. Sectional density is easy to calculate because it simply depends on the bullets caliber and weight. For example, the sectional density of a 175 grain .308 caliber bullet is: 175/7000/.3082 = 0.264 (the bullet weight is divided by 7000 to convert from grains to pounds). Anyone with a pocket calculator can easily figure out the sectional density of any bullet given it’s caliber and weight.

Note that the length of the bearing surface is unimportant to the bullets drag and form factor. Only the nose length, nose profile, meplat diameter, boat tail angle and boat tail length dictate what the drag and form factor of the bullet will be.

IMO you have to figure out what to measure and why... some of the current tools jumble up the what and why. They are useful for deriving insight into the potential consistency of a bullets dimensions...I liken it to the way we use ES/SD numbers for loads...I suspect this is why sorting using current tools works for some people.

Measure weight, bearing surface for consistent MV - what is left over relates to consistent BC (as I understand it).

Hopefully some day someone will come out with a retail available tool that will allow meaningful measurement of a bullets dimensions.

Worth measuring maybe - the usefulness would be greatly improved with tools that measure something meaningful.

 

[Alex Wheeler]

I know that I recently had a lot of bullets that came out .025" shorter than the previous lot. It threw my tune completely out the window. This lot is .012" longer than those. I'm thinking I'm gonna have to retune again...

I would be looking for a more consistant bullet. I am having the same issue with powder. Just opened an 8 lb.er and groups trippled, and I can't tune out the vertical. I could test that for you but I don't have bullets with more than about .003 spread.

 

[gatorman]

The only way you are going to be able to load these bullets is with a seating die that has a ocive
bushing it it if you are going by the ogive measurement only and not the O.A.L of cartrifge..
Even so when if you go this route on the ogive..Your O.A.L is still going to vary,if you follow
my meaning here...I know 1000 yrd shooter who gave up all this stuff and still shhot
fan freaking tastic groups...But do what you want to..You will anyway..John

 

[amlevin]

Just for grins, dump all these bullets back in the box and measure again. Then see how consistent your measurements are.

Some of the variation in measurement may well be in the process and measuring devices), not the bullet.

 

[Keith Glasscock]

I was so surprised by the results that I did that already. I even measured them with my seating depth comparitor to make sure something wasn't amiss. When I remeasured them, I did get a little moving around of the bullets from pile to pile, but the distribution remained very similar and the ES remained the same.

 

[memilanuk]

[quote author=6BRinNZ]...the length of the bearing surface is unimportant to the bullets drag and form factor. Only the nose length, nose profile, meplat diameter, boat tail angle and boat tail length dictate what the drag and form factor of the bullet will be.
[/quote]

Understood... I think the assumption was that given a relatively uniform OAL (sometimes a big assumption), a longer bearing surface would indicate either a shorter boat tail length or nose cone length... both of which are presumed to matter to greater or lesser degrees. Granted, I don't know first-hand what all the dimensions of the bullets in question were, so the example was meant to be purely anecdotal.

 

[ColWhitecakes]

I asked a similar question not long ago about the variation I had with 168gr Amaxs in .308. I eventually settled on just grouping my bullets in to lots that measured the same and were of sufficent number to use at each distance went with it. In the end, I looked at all the varibles that one might find in loading a round and considered how much .001 of bullet length was going to REALLY effect a particular cartridge, given the other possible variations that might exist and my ability to uniform as many of them possible and to what level of precision. There's primer depth, pocket uniformity, flash hole size and deburring, case weight and volume, case length, neck tension, neck thickness, and on and on. That's not even mentioning just exactly how precise the powder is measured, given most scales claim +or- .01 to start with. And lets not forget the primer its self, as there isn't anything you can do about variations in its power out-put, or however you want to refer to it. It's definitely enough to make someone with an obsessive compulsion go insane.

 

[greenron15]

All I know is when I stopped weighing cases,bullets and measuring the ogive at 300 yards my groups got alot larger.

Interesting... I recently started sorting by base-to-ogive; previously sorted primarily on bearing surface.

Either way the bullets I've been sorting have been very consistent, apparently.

Majority (say 50%) @ 0.000", then probably 30-35% @ -0.001, 15-20% @ +0.001... with a few (probably 1-2%) hitting +0.002"

I've been kind of wondering if I'm really going to see any meaningful difference down range for the effort expended, given the relatively tight spread as compared to some of the other numbers I'm hearing.

That said... one person I've talked to who has done a lot of sorting - and testing, with occasional access to Doppler-equipped ranges from what I gather - said that he'd shot rounds with bullets having bearing surfaces that varied by as much as 0.030", and the actual change in BC was fairly low... as in low enough to just about be lost in the noise, in statistical terms.

I know we're all looking for 'perfect', or at least 'better', as compared to straight out of the box... but sometimes I wonder if its really worth it. Like Keith, I've tried testing some variables @ 600yds with results that go one way one time and the other way the next. Actual 1000yd range time is fairly limited for me.

Monte