Meplat trimming & bullet tipping?

Jim:

I respectfully suggest that any computer program that might preduct rersults that fly in the face of the actual results is -- just a computer program model -- nothing more and nothing else.
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Maybe this should be a different thread, I dunno. When you were in school, I'm sure you ran into the coherence theory of truth in Philosophy 101. That's the one that says "truth" is a matter of one thing fitting with other things, rather than "I saw it."

Now at first glance, truth as coherence seems stupid. Or it did to me, as a young kid. But over time, I saw that all science was based on coherence. There are many things we accept because they fit; because the model we have accepted predicts them. The empirical "test" for Einstien's theory of relativity was done exactly once: the phenomena that allow for the test occur infrequently, and the expenditure of resources great. So for relativity theory, we've got one observed instance, and a theory that predicts as true" so much of what has been observed, although those predictions are available in competing theories.

It is still only a theory. Over the past 1,000 years, we've had several theories that seemed to work. They predicted things that did happen. Then we had to abandon them, slowly, grudgingly, with much fighting.

In a small way, that's where we are with the ballistics programs. If things seems to happen they can't account for, we need new ones. On the other hand, if the reported data can be explained, we can keep them. It is both their predictive power and their accuracy that is so important.

Does repointing and trimming meplats work? Yes. Were quibbling over "how much," and I, for one, am desperately hoping that amount falls inside current ballistic theory, or more accurately, that current theory can come up with an explanation for any variance.

* * *

Let me put it a different way. A man is shot & killed & his wallet taken. A 17-year old kid with a long juvenile record is seen at (near?) the crime. He has 10 arrests and one conviction for mugging as a juvenile. He's arrested and charged.

BUT: In all his previous crimes (alleged & convicted), he's used a knife. He's never hurt anybody. What do you feel your chances are as a defense attorney?
 
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Charles:

In the case you describe, my chances might be very good. Did the kid confess? Are there any witnesses? Would his juvenile record even be admissible in whole or in part as a similar transaction -- knife v. gun? Where is the gun? Who is it registered to? If the kid confessed, and the confession passed the Jackson v. Denno criteria -- then you have a conviction. If not, you have to prove him guilty beyond a reasonable doubt -- that is to say he can be found "not guilty" but he does not have to be found "innocent" of the charges.

Where the closed meplats print on the target at 1000 vs. where the unmodified bullets print is kind of a "bullet testimony". Otherwise, you have a jury making a judgment call on what should be and not what actually happened -- without ever knowing the truth for certain -- no matter how they decide the case. I will take the "bullet testimony" everytime and let that be my expert eye-witness testimony.

Jury charge: "Ladies and gentlemen of the jury, this case is about to belong to you. In that regard, the judge will charge you that if you have two theories of how this case happened, and one of them is consistent with the theory propounded by the defense, and the defense theory is not overcome beyond a reasonable doubt by facts or circumstances consistent with the prosecutions theory of the case, then you must return a verdict of "Not Guilty" on that charge. Additionally, I charge you that circumstantial evidence (computer program) can be given such weight as you might consider, but that such circumstantial evidence must be weighed in light of the direct evidence in the case (the actual results of the bullet test). If the circumstantial evidence does not overcome the direct evidence on the same issues, then in that regard, you must give the superior weight to the direct evicence."


"Not Guilty"

Jim Hardy
 
Lynnsghost,

Disappearing posts aside, I'd love to see those numbers. I would expect that trimming would decrease BC (so adding would increase it). That's a little different than pointing though, where you are not just trimming length, but reshaping the nose. Both cases are interesting to me, because it helps us validate what we think we know about the importance of nose shape.

And to weigh in on the software thing... These programs are way too simplistic to predict with much precision. (They're almost litterally F= ma, mathematically speaking). But what they can do is provide us with a framework from which to work. If bullets hit 18" high in real life, that's what they do. If we can replicate something approximating that with software, it can help us figure out if there is a way to make them hit 24" high. Software can help us figure out what matters. As a professor of mine once said, "we analyze for insights, not numbers."
 
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Charles:

I have found the old threads. I don't know how to attach them here, but it would be very interesting in light of the current thread and 20/20 hindsight.

The first thread of interest was started by John Kielly on 12-29-07, entitled "Pointing Tools -- Whats the deal?

The second thread was started by Bryan Litz on 3-01-07, entitled "Effects of meplat trimming"

The third thread was started by John Whidden on 3-13-07, entitled "New bullet point (tipping) tool" This is the thread where Jason Baney posted the details and the PICTURES of the testing he did at the PA club with the bullets I pointed for him. In this thread, Bryan Litz also does an analysis showing that there was an increase of 9.2% in G7 BC and 11.5 % less wind drift with the closed meplats in Jason's testing with the 106 Clinch River.

These threads flesh out about all you have to know. Start with the bottom line result and do reverse engineering, if you will. Many questions and answers and doubters in the thread. All gone by the wayside when looking at the history of the closed meplat in competition. In fact, the threads will reveal that I had a pending NRA 600 yard prone metalic sight record pending at the time. But, it does not show that I broke Mid Tompkin's then existing 9 year old Sr. prone record for Irons at 1000 yards at Camp Butner (105 Degree heat in the same match at Charles Ballard set the F-Class Record) with a 200-14X.

It is all here -- the real results -- and calculations by Bryan Litz, an actual rocket scientist!

There is one correction I may have to make. When I shot the 45Xs at Camp Butner one December, early in my prone career, the thread shows that it may have been with BIB 6mm 105s (not 108s) with the meplats closed. Not for sure if the BIB flat base or the 106 CR. I know that I did shoot the BIBs in a prone match at Ft. Benning out of my 6mm prone gun for a 12X on one string at 1000.

These old threads are very enlightening. If you could somehow attach them, or JBs test, or the link to this thread, it would be much appreciated.

Thanks in advance,
Jim Hardy
 
Here are the links

Pointing tool
http://benchrest.com/showthread.php?48141-Pointing-tools-What-s-the-deal&highlight=Pointing+Tools

Effects of Meplat Trimming
http://benchrest.com/showthread.php...Trimming&highlight=Effects+of+meplat+trimming

New Bullet Pointing (tipping tool)
http://benchrest.com/showthread.php?40814-New-Bullet-Pointing-(Tipping)-Tool&highlight

I do have one question, when refering to pointing i am making the assumption we are talking about reducing the meplat by 50% from .060 to .030. is this the general concensus or are we talking about closing the point. (with the exception of closing the point like Lawn Dawg as he has a pointing system we all want but can't get)
 
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R.G. Robinett said:
John, because the meplat diameter (original Sierra 155) was [comparatively] HUGE.:p The original 155 Sierra Palma bullet (don't know the Cat. numbers) had a real-world BC only equal to my 155 FLAT-BASE!:eek: Next to mass, reducing the meplat diameter is the fastest way to BC. As I recall - a dangerous proposition - McCoy pointed out that once the meplat diameter is below a defined percentage of caliber (sorry I cannot recall the %), 'accuracy' suffers . . . it seems that drag IS a stabilizing force.:confused::p Mr. Childs extreme 'tipping' experiment may have provided empirical evidence that a SHARP point is undesirable. RG
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Hi Randy I hope all is well and need to talk to you about some 108s,but to the subject, I had talked with Henry about his sharp point tests as well and presented the theory that the flowfield was too close to the tip causing a pitch of the tip which could possibly explain the random dispersion that henry was seeing but I could never prove that though, But has always been in my mind when it comes to tipping my own bullets.I would certainly like to see a test with pointed bullets that would show not only bc gain but consistancy of bc is at least better from bullet to bullet and that I could do it without distorting the ogive and or the folds of the jacket. I just get the feeling I am introducing more varibles into the bullet by pointing but I could certainly be wrong on that thinking . Tim in Tx
 
Trevor60 said:
I do have one question, when refering to pointing i am making the assumption we are talking about reducing the meplat by 50% from .060 to .030. is this the general concensus or are we talking about closing the point. (with the exception of closing the point like Lawn Dawg as he has a pointing system we all want but can't get)
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Pretty much. The instructions that come with the Whidden die *suggest* that you can close the tip until further work creates a bit of a bulge, which occurs just behind the where the die begins it's work. Alternatively, if you can get that far, when the tip is completely closed -- metal touching metal, the meplat still has some diameter -- the thickness of the jacket wall, plus a little. Jim's setup allows him to go farther, & I'd guess he's not run into the problems Henry Childs / Tim-in-Texas thought they had found.

Just what that (those) diameter(s) us normal folk are limited to is a trifle hard to measure, but .030 on a .30 is pretty close.

On another front, my wife got the tire changed, but then her kid sister came into town. I've just now gotten the Pejsa program running. I'll give the numbers later, but as a BTW, everything seem to be fitting fairly well.

P.S., Jim's a lawyer, not a gardener -- it is Law Dawg, not Lawn Dawg. Probably that was just a typo, but for those who don't know Jim . . .
 
For you guys in the KNOW
How many top long range shooters are using meplat trimming and pointing( just rough percentage).
Personally I have never shot in a single competition but would like to try soon.So, I have been giving a great deal of thought to all things related to long range accuracy.I have been thinking of trimming and pointing BUT does it really make any difference? I mean the bullet spins at very high revolutions so it should all balance out( as far as group size)Personally I am only concerned with group size. Perhaps there is more to it.Am I wrong?
 
canuck said:
For you guys in the KNOW
How many top long range shooters are using meplat trimming and pointing( just rough percentage).
Personally I have never shot in a single competition but would like to try soon.So, I have been giving a great deal of thought to all things related to long range accuracy.I have been thinking of trimming and pointing BUT does it really make any difference? I mean the bullet spins at very high revolutions so it should all balance out( as far as group size)Personally I am only concerned with group size. Perhaps there is more to it.Am I wrong?
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Check out this poll...will give you an idea what is going on with bullet tipping.

http://benchrest.com/showthread.php?74867-Poll-on-who-tips-and-who-does-NOT-for-1K-shooting.
 
400 yds is not long enough distance to see the benefits of uniforming the meplat and tipping. My 2cents worth on this discussion as it applies to the custom made bullet I shot (6.5mm 136 grain VLD). Shooting 1000yd IBS matches in 2009 and first 4 matches of 2010 I UM and pointed the bullets and shot quite well for me. Then I got the bright idea that all I needed to do was to point the bullets and get even more bc. My shooting results became worse. I have since gone back to doing both for 2011 and it seems that accuracy is restored. My theory for these already long ogive bullets when made even longer it diminished accuracy.
 
Charles: You are right about going too far with the pointing die, I have a 309 bushing I use to make sure all my bullets go through with the same feel. And when trying to get a nicer point, I found they would no longer go through the bushing. What I think happened was just a little too much pressure with the press caused the bullet to bulge at the front of the boat tail. Feed back from anyone on that? And another thing I've wanted to ask was every time you trim the Meplat , aren't you taking BC away from the bullet and then trying to put it back by tipping? (I don't get it)

Joe Salt
 
joe, yes this happened when i tried to close the tip to a point when I first started tipping bullets .but i found a way to close to a point and not distort the bullet in any way.It has worked with good results last match my dad shot these in heavy, and I shot them in both classes. 5 inch groups for us in heavy with very tight 8-9 shot knots.Talk to you at the match this weekend, to much typing for me here!By the way I use the hoover trimming set up.
 
slw see you this weekend, you show me your's I'll show you mine! Hope charles doesn't delete this. Found ot my first time I tryed it.

Joe Salt
 
I find the same thing. I am using the Hoover die and you can only go so far with pointing, otherwise the jacket will bulge.

Use a little imperial wax on the bullet tip if not doing so already, helps close the tip a bit better.
 
OK guys

I've made arrangements to shoot some bullets at a range with doppler radar. It's not a high wattage system but will suffice for this test. Here's what I need like yesterday.

30 cal. bullets on the heavy side suitable to be shot in a magnum size case. I need 20 each in the following categories. All from the same lot.

1. stock, nothing done to them
2. meplats cautiously trimmed
3. meplats trimmed and pointed
4. pointed only



Dave Tooley
 
I have 2 end mills from John Hoover so I can meplat trim the longer bullets with one and the shorter bullets with the other.When pointing make sure you are not pointing too much. Measure base to ogive before and after pointing to make sure you are not shortening the B-O measurement. I recommend Hoover's trimmer and pointer. He will help you with all these questions.
 
marion packett said:
I have 2 end mills from John Hoover so I can meplat trim the longer bullets with one and the shorter bullets with the other.When pointing make sure you are not pointing too much. Measure base to ogive before and after pointing to make sure you are not shortening the B-O measurement. I recommend Hoover's trimmer and pointer. He will help you with all these questions.
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That's a good idea having 2 endmills. I will ask John the next time I see him about getting a second one for myself. I keep having to adjust for different sorted lots.

I was also thinking, a micrometer adjustment on the trimmer would be nice as well.
 
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