A level 2 bullet sorting question

T

tricrown

Guest
Some years back I tried to answer this question. If one bullet has .010” more bearing surface than another bullet from that same lot. Where does that bearing surface reside? Is it .010” higher towards the tip, lower towards the base, split even, or erratic? To try and answer that I had a tool made for my comparator that was nothing but a small hole so I could re-sort already bearing surface sorted bullets measuring to a consistent small diameter way up on the bullet. Figuring similar shaped bullets will have a more consistent BC. It is something like what Bob Green’s tool does. But my limited efforts at re-sorting already bearing surface sorted bullets were all as close as the capabilities of my caliber were to measure that I soon gave up. Turning the tool into another experiment.

A year or so later there was a thread in one of these forums where some custom bullet makers were saying that with their bullets (don’t remember if it was a specific kind of bullet) the part above the ogive was always shaped the same. So that would mean any difference in bearing surface has to come from the bottom section of the bullet. Therefore the base to ogive readings in bearing surface sorted bullets should all be the same? So I’m wondering what’s the widest variation in base to ogive readings you ever got between bullets that you’ve already sorted for bearing surface? Have you noticed any trends? Like among bullet makers (custom hand as compared to machine made), shapes, or the number of bullets that are way off?
 
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tricrown said:
Some years back I tried to answer this question. If one bullet has .010” more bearing surface than another bullet from that same lot. Where does that bearing surface reside? Is it .010” higher towards the tip, lower towards the base, split even, or erratic? To try and answer that I had a tool made for my comparator that was nothing but a small hole so I could re-sort already bearing surface sorted bullets measuring to a consistent small diameter way up on the bullet. Figuring similar shaped bullets will have a more consistent BC. It is something like what Bob Green’s tool does. But my limited efforts at re-sorting already bearing surface sorted bullets were all as close as the capabilities of my caliber were to measure that I soon gave up. Turning the tool into another experiment.


A year or so later there was a thread in one of these forums where some custom bullet makers were saying that with their bullets (don’t remember if it was a specific kind of bullet) the part above the ogive was always shaped the same. So that would mean any difference in bearing surface has to come from the bottom section of the bullet. Therefore the base to ogive readings in bearing surface sorted bullets should all be the same? So I’m wondering what’s the widest variation in base to ogive readings you ever got between bullets that you’ve already sorted for bearing surface? Have you noticed any trends? Like among bullet makers (custom hand as compared to machine made), shapes, or the number of bullets that are way off?
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I think you have your terms mixed up. You're saying one thing but I think you mean another.

Bearing surface: The part of the bullet that is more or less one diameter. That part that "Bears" On the bore of the rifle.

Ogive: Simply put, the shaped part of the front of the bullet which resides in front of the bearing surface.

Base: To me, this means the flat bottom of the bullet. Others might think it includes some part of the boattail if it exists, or the radii at the lower end of the jacket. I do not.

Boattail: The angled part of the bullet at the rear.

Boattail junction: Where the boattail meets the bearing surface.

Ogive Junction: Where the ogive meets the bearing surface.

Meplat: Front flat tip of the bullet (flat part on a hollow point)

You might consider editing your question if you are still unsure of the answer. But, to answer the question about bearing surface, I've seen >.010 of variation. Yes the bearing surfaces can an do vary some, but that will vary depending on the lot of bullets. Some are better than others, as is always true.

Consider the die itself. It is two pieces which shape the bullet. The front part and back part are the same shape every time. There isn't much way for the ogive or boattail to vary.

Now, if the jacket is longer, it can squish up and out of the meplat hole in the die. In this case, overall length is longer. At that point though, the meplat size is very consistent because it has been forced into a cylindrical hole and is sticking out (rarely happens) If the dies do not collapse all the way, the bearing surface is longer.

At no point will the boattails vary measurably.

The geometric assumptions you're making are right on. But you need to measure the bullets to find out where the problems are. Depending on the bullets you have, there may not be much variation to measure.
 
If you measure base to Ogive on a 30 caliber bullet with a 30 caliber comparator then use a 6mm comparator insert and a 22 caliber comparator insert you will quickly switch to custom bullets made with a single die.I too have read that the ogive was very consistent but whom ever said that was either full of beans or shooting tangent ogve bullets in my humble opinion.

I have seen 0.023 worth of variation in the bearing surface from the same lot# of bullets from the big manufacturers in a single box.
If your not seating your bullets using a comparator you will never get them to the same length.There is simply too much variation in the ogive shape of non-custom bullets.
Lynn
 
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4Mesh said:
At no point will the boattails vary measurably.
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Phil, I've found them to not be concentric. Now this was measured with a Jeunke, which involves some controversy. But the measurements of mine (240 Sierras) and Joel's (also 240 Sierras) shot as measured -- Joel's shot better, in either rifle.

Well, small sample size. But *something* goes on with boattails. Both the BIBs flatbase in .30 and the Clinch River 6.5mm flatbase grouped the best of their calibers at 1,000 yards. (Both calibers as tested by me, Tooley, and Shelp; the .30 BIBs by a lot of people, as you well know).
 
Charles E said:
Phil, I've found them to not be concentric. Now this was measured with a Jeunke, which involves some controversy. But the measurements of mine (240 Sierras) and Joel's (also 240 Sierras) shot as measured -- Joel's shot better, in either rifle.

Well, small sample size. But *something* goes on with boattails. Both the BIBs flatbase in .30 and the Clinch River 6.5mm flatbase grouped the best of their calibers at 1,000 yards. (Both calibers as tested by me, Tooley, and Shelp; the .30 BIBs by a lot of people, as you well know).
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Interesting Charles,

Would that mean than the boattail cup part of the die was made eccentric and they are all consistent?

I have measured mostly Bergers, Knights, JLK's in the day, and they have been pretty nice. Mostly within the limits of my measuring ability, which is pretty close. TIR as I recall, never exceeded .0004 anywhere tip to bt. That doesn't leave much for the bt to be out of round. I never did check that on the shorter bt of a Sierra.
 
Most boattails are formed when the core, under pressure from the core seating punch, pushes the base end of the jacket to the bottom of the die and then stretches the core out like a balloon to fill the boattail cavity of the die. In most cases this probably results in a pretty symmetrical boattail jacket thickness. If the domed end of the empty jacket isn't perfect, then maybe the resulting boattail has less than perfect core concentricity and cg.

At least one custom bullet maker, Clinch River, adds a step in the process and forms the boattail in the empty jacket with a boattail shaped punch before the core is seated. Performance of those bullets suggests that this extra process may increase uniformity and resulting accuracy.

I doubt that externally measuring bullet boattails will reveal a lack of concentricity, but a Juenke might reveal variations in jacket thickness at the boattail.

Greg
 
Greg Culpepper said:
At least one custom bullet maker, Clinch River, adds a step in the process and forms the boattail in the empty jacket with a boattail shaped punch before the core is seated.
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R.G. Robinett does the same. Perhaps others as well.

I doubt that externally measuring bullet boattails will reveal a lack of concentricity, but a Juenke might reveal variations in jacket thickness at the boattail.
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Yes, the Jeunke is showing something -- the question is what. Berger's testing of the unit showed it isn't measuring what it is suppose to. Still, I use mine, just not for the original, stated purpose.

BTW, I forgot to mention with the BIBs and CR flatbase bulets: The other thing these have in common is they use a tangent ogive, not a secant. The BIBS .30 caliber is a 10-caliber tangent. IIRC, the CR 140-grain 6.5 is an 11-caliber tangent. It may be, that in spite of the theoretical advantages of secant ogives, when it come to manufacturing, the tangent ogive is easier to form with complete consistency.

Another by-the-way: Is Greg Sigmund still making bullets?
 
Charles, I am still a believer in the Juenkie, but I conducted several test that lead me to not trust in it as much as I once did. I sorted bullets by weight, diameter,length, which included bearing surface lengths and ogive to bearing surface, and then the Juenkie. Needless to say, I had several piles of bullets. I took bullets that had good Juenkie unit numbers and shot them compared to bad unit numbers. To make a long story short, some that were 15 to 20 Dev. units, shot better than 0 to 5 Dev. units. I found that bullets that ran the same place on the scale of Dev. units either high or low, shot better groups than those that were low devations or even bullets that didnt even move the needle. I also ran all bullets with the balls on the boat tail and bearing surface, checking both ways. To sum up the test, I didnt really prove anything. I still like the Jeunkie, I think it is a mind thing! I also conducted some test in which I bent the tips of bullets, cut off the meplats,and just about anything bad that could be done. I shot the bullets through a wireless camera set-up so I could see each impact on target, it didnt affect the groups as bad as you would think.I then "sratched" the base with a file and shot them. The accuracy was affected drasticly. In my opinion, for what it is worth, more concentration on the bases and boat tails seemes to be the most important. I have also found that the diameter of the bearing surfaces, seemes to be more important tha weight and length. I just thought I would share some of this with you since you asked about the Jeunkie. Shannon L
 
Charles,

I don't think Greg has made bullets for sale in quite a while. He's got a "paying" job and spending a lot of time being a Dad.

Not to quible, but CR's are 13-caliber secant whether 6mm, 6.5mm or 30.

Greg
 
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Shannon,

rem300ack said:
I found that bullets that ran the same place on the scale of Dev. units, either high or low, shot better groups than those that were low deviations or even bullets that didn't even move the needle.
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Yes! That is the primary thing I use the Jeunke for.


In my opinion, for what it is worth, more concentration on the bases and boat tails seemes to be the most important. I have also found that the diameter of the bearing surfaces, seemes to be more important than weight and length.
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A second big yes. It is surprising, as you'd thing the pressure in the barrel would "conform" all the bearing surfaces to the same diameter -- it probably does, but somehow the "prediction" of the Jeunke works when measuring this.

BTW, are you going to make the banquet Saturday?

Edit:

Greg -- are you sure the 140-grain 6.5 flatbase was 13-tangent? Believe Tooley designed the bullet, and that's a bit high for one of Dave's designs.

But it could well be; my menory isn't what it once was. Another IIRC -- I think Tooley & maybe Shelp paid for that die, then Greg (Sigmund) paid them back in bullets. Sure would be nice to have that die, if Clinch River is not going to make any more bullets.
 
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I dont think I will be able to make it. I am covered up with work and just dont think I can make it happen.
 
Greg Culpepper said:
I doubt that externally measuring bullet boattails will reveal a lack of concentricity, but a Juenke might reveal variations in jacket thickness at the boattail.

Greg
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I have always figured that the jacket and core have virtually no rebound, so they should form to whatever reverse image the die provides. Now, as to how concentric that lead is inside, that's another story. But I have no control over it even if it is wrong. I have never believed a Junke machine could differentiate jacket thickness, so on that I am skeptical. I think I measure much of what it does, I just do it differently. I have no doubt it gives valuable data though.

Shannon,
In my experience, I came to believe that mis-shapen bullets actually shot better than perfect ones. Just slightly mis-shapen though. I have a theory on why but it's just a wild ass guess, and my guesses are liable to get me into trouble. I'm surprised this thread has made it 2 days without someone jumping in and saying that bullet sorting is a waste of time...
 
4Mesh said:
. . . I'm surprised this thread has made it 2 days without someone jumping in and saying that bullet sorting is a waste of time...
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Phil, IMSLTHO, it kind of depends on where you're starting from. If you're pretty much getting 10-shot groups that measure 8 inches on mild days, yeah, it's a waste of time. You have bigger problems. If you're getting 5 inch groups and want to move groups into the 4s, probably something you need to do, even if we don't know exactly which measurements are important -- i.e., why.
 
Charles E said:
If you're getting 5 inch groups and want to move groups into the 4s, probably something you need to do, even if we don't know exactly which measurements are important -- i.e., why.
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Charles,
I think you have a pretty good idea which ones matter and which ones don't.
 
4Mesh said:
I'm surprised this thread has made it 2 days without someone jumping in and saying that bullet sorting is a waste of time...
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Phil, I just can't let this opportunity go. I have what's left of a buy of 3000 bullets of which I thought I'd found 10 in the first 500 that could be segregated by bearing surface length. I set them back in the box but out side the bag. When I got to the second box I remeasured those 10 culls and found that I had miss-measured them and they were the same as the next box. Since then I've quit measuring each one but I have done some random sampling that supports my opinion that there is probably not a single bullet out of those 3000 that could be segregated with my tools.

Another discussion here more than a year ago led me to weigh a sample of twenty. I don't bother sorting by weight but I'm accustomed to seeing 0.2 or 0.3 grain spreads on good 6mm bullets meaning bullets that have a 0.003 " extreme spread for bearing surface length. This sample showed 0.02 gr variation on a Denver 603 D. So I'm wondering if very uniform core weights lead to very uniform bearing surface lengths. Sometime I'll weigh groups of bullets that have been segregated for bearing surface length and see if they are also organized by weight.

Oh, these extremely uniform bullets are Sierra 6mm SMK 107's and they shoot really well.

So for this lot of bullets anyway, "bullet sorting is a waste of time". Ha! Got to say it.

Greg
 
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Greg,
I am not going to disagree that sorting by bearing surface on most decent bullets is probably a waste of time. First, where people measure them is a near impossible spot to get an accurate measurement. Next, about all it tells you is weather or not that manufacturer sticks all bullets in one bin, then measures out 100 and calls it a lot.

When it comes to determining what matters and what doesn't, I use a basic mathematical assumption. I look at what my errors are as a relationship to the total. If you're using a 105 and find .3 gn spreads, that's roughly .3%

Now express that as a percentage of what is the smallest measurable error on the target. Meaning for any given error, what does it take before I see it. Can I quantify 1gn variation in powder as vertical dispersion? Ok, how much is it. What % does my weighing accuracy represent? Ok now I know what I am giving up in powder weighing at my chosen resolution. There is not a doubt in my mind that 1 gn weight difference in otherwise identical bullets is easy to see at 1K. Is in my guns anyway. At that point, I figure that shooting .3gn difference in bullet weight, (altering BC) is worth a measurable vertical, and I'm not gonna do it. Now if someone else wants to, that's fine by me.

I sort by a lot of criteria, and every single one has been quantified. Now, I'll agree bearing surface is only important to those people who have bullets that vary on bearing surface. I don't think the big vendors of our match bullets have that sort of issue. They most certainly have other issues tho.
 
Lynn said:
4Mesh
Are you telling us your pointing your bullets without sorting them first?
Lynn
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No Lynn, and honestly I can't imagine what I said above that would make you think I don't sort.

But, I suppose a person could look at what I do and say that I do sort by bearing surface, even though I do not measure what most people call bearing surface. In a roundabout way, I guess I get there. And I agree with what you're saying in that pointing without first sorting, is a waste of time. In fact, possibly counterproductive. Unless of course you start with a bullet that is the biological clone of all its sibling. Not many folks have them, but some do. Again, if it were me, those bullets wouldn't get pointed either. Matt is correct though, I think pointing is unnecessary. It just means you'd have more work of another sort. There is no free lunch. If you want consistent bullets, you have to make them so, either in production, post production, or sorting.
 
Phil, you're right about the never ending-chain of events, once you start. The reason I point is because I trim meplats. The reason I trim meplats is because it's pretty far up there on the number of things that can affect BC.
 
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