Purpose of bullet sorting

[smithcollector]

is the purpose of sorting bullets based on length, whether base to ogive or other factor, to help control consistent seating depth, or do differences in these measurements impart different ballistic characteristics?

If I have two batches of bullets sorted by length, do I load them with the same powder and die setting, and just keep them separate, or is separate load data needed for each batch?

I'm just wondering if the ultimate goal is to have consistent jump, or is there another goal?

 

[Patch700]

Bearing surface area is another.. If the difference in length is due to a longer ogive profile that is one thing.... if it is due a longer surface area that will be in contact with the bore , that may have greater consequences for not keeping them segregated.

 

[mikecr]

It does not affect seating relationship to lands.

 

[dmoran]

smithcollector -
Myself I qualify/segregate my bullets for equalization gains to both seating and ballistic coefficient consistency.

mike -
"It does not affect seating relationship to lands"
But it does effect the amount of bullet seated (load density) as well as the coefficient (BC).
And is why I myself segregate to the ogive first, then to the seater stem diameter, then the OAL.

My 2-Cents
Donovan

 

[Ned Ludd]

In my hands, seating depth for jumped bullets can be changed as much as .010" in either direction without affecting velocity (pressure) to the extent that my chronograph can reliably detect the difference. For that reason, I much less concerned with small changes in the amount of shank in the neck and much more concerned with the actual seating depth. A few thousandths difference in the amount of shank in the neck has little impact, but changes of a few thousandths in seating depth can have a huge impact on precision. Sorting bullets base to ogive by typical methods may help to keep a uniform amount of shank in the neck, but I have found it to be of limited use otherwise.

To obtain the best consistency in seating depth without having to constantly fiddle around with the seating die micrometer setting, the critical region for bullet sorting lies between where the seating die stem contacts the bullet ogive and where the caliper insert seats just above the bearing surface (see cartoon below). Tools such as Bob Green's Comparator (link below) can be used to sort bullets based on the dimensions of this region.

http://greensrifles.com/New_Products.html

 

[mikecr]

OP is talking about bullet LENGTHs, not ogive radius variance.
And normal variances in whatever you think you're measuring in BTO, can be meaningless to either load density, neck tension, seating, or BC. At the same time, zero apparent BTO variance can mask an actual deviation. For example, an apparent shift in bearing might actually be caused by base angle shift. This, not affecting seating, or tension, load density, and possibly not even BC. Then there is as likely more than one variance, with some countering others, given generalized measurements(like BTO).

Is there one test put out there that shows any cause/affect in this? And did they break it down to what's what & why?
Personally, I doubt there is, or will be.

To do this, you would have to separate ->
Bearing (which stems from qualified base angle AND qualified nose datum/qualified ogive radius)
From end diameter
From base length
Meplats and nose lengths would also have to be measured for BC calcs.
Each of these parameters are separate and contributing different drag.

For bearing variance itself, just run the numbers in QL and you will see just what you'll see across a chronograph.
Nothing from it. Completely insignificant.
The single biggest affect to BC in bullet build variances comes from meplats, and we don't talk about measuring these at all. I guess, because nobody has put out a meplat measuring toy yet..

 

[Ned Ludd]

MIke - my take was that the the OP was asking about bullet sorting in general, either by OAL, BTO, or any other method. I think you and I are in agreement that sorting by BTO measurement is fairly useless. Too many other critical dimensional measurements affect precision to a much larger degree. I sort bullets for two primary reasons, 1) for pointing purposes and 2) for consistent seating depth, which, along with consistent neck tension, are probably the two most important things that can be reliably measured for consistency to obtain optimal precision. Bullet sorting for consistent seating depth can be carried out pretty effectively using Bob's tool, which is why I mentioned it.

 

[smithcollector]

The earlier thread about the Bob Green Comparator was actually what got me thinking, and revealed a big flaw in my previous loading technique, which was to sort BtO, but then not adjust my seating die, causing significant seating depth differences with Sierra 142s. My take from the above is similar length bullets will seat similarly, but I will need to adjust my seating die when I switch to a new sorted batch. This afternoon I loaded 100 rounds, with Sierra 142s, consisting of 25 rounds each with bullets with extreme BtO varying 14 thou. They are now all seated to the same depth measured base of brass to wherever the Stoney point gauge hits the bullet. Hopefully these will shoot to the same point of impact, we will find out tomorrow.

 

[Ned Ludd]

With regard to consistent seating depth, sorting bullets by OAL will likely be a noticeable improvement over sorting by BTO, if not quite as good as sorting with Bob's tool. Good luck at the range and let us know how they shoot.

 

[jim_k]

Don't do it. It almost certainly will not make any difference.

 

[JohnKielly]

I sort by eyeballing meplat size after I trim it. Seems to give all the correlation I need.

 

[Jet]

Smithcollector

Please keep us updated on your results. You are doing what will lead to smaller groups. Doing research, asking questions and most importantly verifying by testing yourself. Keep good notes and good shooting.

Rich

 

[johara1]

OP is talking about bullet LENGTHs, not ogive radius variance.
And normal variances in whatever you think you're measuring in BTO, can be meaningless to either load density, neck tension, seating, or BC. At the same time, no BTO variance can mask an actual deviation. For example, an apparent shift in bearing might actually be caused by base angle shift. This, not affecting seating, or tension, load density, and possibly not even BC. Then there is as likely more than one variance, with some countering others, given generalized measurements(like BTO).

Is there one test put out there that shows any cause/affect in this? And did they break it down to what's what & why?
Personally, I doubt there is, or will be.

To do this, you would have to separate ->
Bearing (which stems from qualified base angle AND qualified nose datum/qualified ogive radius)
From end diameter
From base length
Meplats and nose lengths would also have to be measured for BC calcs.
Each of these parameters are separate and contributing different drag.

For bearing variance itself, just run the numbers in QL and you will see just what you'll see across a chronograph.
Nothing from it. Completely insignificant.
The single biggest affect to BC in bullet build variances comes from meplats, and we don't talk about measuring these at all. I guess, because nobody has put out a meplat measuring toy yet..

You base all your findings on QL. ? I have found theses things matter, if you are looking for small groups at long range and to discount the findings that we found on paper to what QL. says is not fact based, only theory a bunch of ball park numbers to get you going in the right direction. You had better read what people like Donovan and others say to be fact, and use QL. for reference only....... jim

 

[mikecr]

I agree that there is more to results than can be seen across a chronograph, or as predicted with load calibrated QL.
Seating testing makes that clear, as you can nearly double group size with seating adjustments that won't show on a chronograph.
I'm just trying to get folks thinking about merchandising and get them to consider the specifics of what they're doing, and reason through it(rather than assume through it). This could make a difference for them.

If someone has separated and quantified cause & affect with BTO, I would be interested in reading about that.
I don't expect it, I'd just be interested.
I do picture such an endeavor as very difficult to declare anything with.

Consider past seating declarations -that were always wrong. How did we come to believe that VLDs had to be jammed to shoot? Was it with testing, and/or with reasoning? No. It stemmed from broad declarations by competitors, having no real basis whatsoever.

You had better read what people like Donovan and others say to be fact

No. I better think. Everybody at this forum needs to think, to separate logical reasoning from potential flimflammeries.

 

[PMA3]

I have to agree with mikecr that meplat diameter is the most important bullet dimension that affects shot-to-shot BC consistency. As Mike stated, no one has made a "toy" to check this dimension, but you can get pretty consistent meplats if you use bullets that are custom made like the Bart's 105 Infinity bullet with an advertised meplat of .040".
I checked about 100 of these under a microscope and they all "looked" very consistent.....no way to definitely check the size, but under the scope they all looked real close and I used a .040" needle as a double check. I had an overall length for this lot of a 1000 measure 1.232-1.243. I sorted into 4 sub lots of .003", then tipped each sub lot separately .025" in order to close up the meplat to approx. .015". This reduced my 1000 yard clicks by 4 (100 to 96) and these tipped bullets shot 10" flatter than the bullets that were not tipped. I also use the Bob Green tool as my final sorting parameter. Factory bullets had meplat diameters all over the place, so the switch to Bart's was a no brainer for my purpose of 1000 yd br.

 

[zipollini]

Take a look at this. This is what Brian Litz has to say about bullet sorting.

 

[dmoran]

With regard to consistent seating depth, sorting bullets by OAL will likely be a noticeable improvement over sorting by BTO, if not quite as good as sorting with Bob's tool. Good luck at the range and let us know how they shoot.

For bullet equality, my experience is that BTO is the most critical length measurement.
For seating equality, ogive to the seater diameter (BG).
Variation in OAL having the least significance of the 3, but is important to me as well.
Just my 2-Cents and experience.
Donovan

 

[Mozella]

I sort my bullets, but based on weight. Measuring BTO is quicker and easier, but when I measure my Berger VLDs I notice hardly any variation at all. So small in fact that I find it hard to believe that it's a significant criteria. But I notice a surprisingly large difference in weight. My .223 Berger VLD 90's vary by a full tenth of a grain, which is easy to measure on my scale with a .02gr resolution. I sort them into three piles, light, medium, and heavy, for my three F/TR 20-shot strings with an occasional odd ball heavy/light bullet tossed into the "fouler round" bin.

It's hard to argue with Mr. Litz and if he says sorting on BTO is important I take notice. But he also says annealing every time didn't show up as significant during his careful testing. But my records show an improvement in precision after I started annealing every time. I do careful testing too, so I'll continue to anneal.

A good deal of the sort of stuff we do in our reloading rooms is obviously associated with tiny theoretical improvements in precision at the target. Yes, we can measure stuff in our reloading room to very fine tolerances. And we can measure the holes in the target with high resolution too. But when you consider the conditions under which we deliver our test rounds to the target, it's hard to pretend that discovering the genuine, no-BS, real down-to-earth truth is an easy thing.

 

[johara1]

If base to ogive vary i don't go any further..... over all length vary a lot is another failure, i sort by bearing surface. then i trim and pointing careful not to change any measurement on the bullet, meoplats are a non issue do to pointing. They are all the same....... jim

 

[mikecr]

It's hard to argue with Mr. Litz and if he says sorting on BTO is important I take notice.

Bryan never described specific cause/affect aspects of BTO.
He also did not state that he sorts on BTO.

He was cornered to reply on what sorting would be most significant(if sorting 'one way'), and he took that w/resp to weight, OAL, and BTO. These are simply common measures coming to his mind, I'm sure.
He felt OAL measurements would be poor & misleading due to the meplat conditions.
Weight, in normal variance(not an anomaly), was insignificant in his view.
That left BTO, but without actual basis. Just that it indicates inconsistencies in form(none specifically mentioned).

So if you act on this, then what specifically will you 'take notice' of?
Let's say you measure & sort 50 bullets with the same BTO. But unknown to you(because the measure is so general), 3 of the bullets have longer bearing surface with corresponding longer ogive radius and corresponding larger meplat for nose lengths, due to a forming inconsistency. Well, those 3 in your carefully matched pile hold different BCs than the other 47. And consider this, some of those you culled out actually matched in BC with those 47. It's just that you don't know it.
The same holds with weight(in itself) differences, and it's much like matching brass by weight instead of actual capacity. Right?

Truly, the only way to do this sorting correctly is to separate each measure of every single bullet attribute, consider them separately for what they cause individually, and then combine all contributions to know what is different between bullets.
Otherwise, you're merely taking shortcuts with fairly blind actions.
I couldn't say that you're doing more harm than good. But I can suggest you're not doing what you think you are.
I'm confident in this because today we're so far from comprehensive bullet measure.
We need something like this: