G
gt40
Guest
Got it Matt. Sent one back at ya.
Got it Matt. Sent one back at ya.
D
Damon
Guest
Perhaps someone can answer a couple questions, as I've not used these gadgets.
What is the claimed/hoped for (approximate) BC improvement from this sort of thing, and how does it compare with the accuracy of BC measurements in general (as described in Bryan Litz's book, and in the '97 Precision Shooting Annual by McCoy)? In other words, is the uncertainty of measurement much greater than the expected improvement?
And am I the only one worried about introducing defects with these extra operations?
What is the claimed/hoped for (approximate) BC improvement from this sort of thing, and how does it compare with the accuracy of BC measurements in general (as described in Bryan Litz's book, and in the '97 Precision Shooting Annual by McCoy)? In other words, is the uncertainty of measurement much greater than the expected improvement?
And am I the only one worried about introducing defects with these extra operations?
Yeah, I think you're the only one. I had some worries about the repoint die-- never the meplat trimmer -- but they were removed when I got the Whidden. You can close the points as little as you like, testing along the way.
The repoint dies have been around a long time. Speedy Gonzales was doing this in the 1990s, -- maybe earlier -- for his 6mm long-range varmint rifles. But he tested them, and saw only gains. He made his out of carbide, and as with most things he made, the point was dead nuts. Not to say you couldn't make one that was out -- the more universal the die, the more it would seem error could creep in.
The questions in my mind are, how much and how predictable? As I said, I've repointed one bullet that struck about the same height. Group was about the same, too.
OK, definitely anecdotal here 
but Henry Childs sent me some 6mm bullet's he'd modified by drilling/retipping w/aluminum and having the AL tips ground to a NEEDLE point. These things are so sharp he sent them to me individually mounted with tip protectors.
He tested them on his 43 setup
He fired them for effect,
and he even shot a deer with them!
But he wrote them off as a loss for competition purposes.
al
but Henry Childs sent me some 6mm bullet's he'd modified by drilling/retipping w/aluminum and having the AL tips ground to a NEEDLE point. These things are so sharp he sent them to me individually mounted with tip protectors.He tested them on his 43 setup
He fired them for effect,
and he even shot a deer with them!
But he wrote them off as a loss for competition purposes.
al
John Kielly
Shari's fan club
Gotta be something going for pointing - besides hype. Why did Sierra go to that trouble of pointing their 155 grain 2156 .308 pill & kick up their & the shooters' costs if there wasn't a benefit?
Sure it's only got their BC up to round about the same as the 155s from Berger, Lapua & HBC but at least they're back in the ballgame.
Sure it's only got their BC up to round about the same as the 155s from Berger, Lapua & HBC but at least they're back in the ballgame.
R.G. Robinett
"That'll never work."
John, because the meplat diameter (original Sierra 155) was [comparatively] HUGE.
The original 155 Sierra Palma bullet (don't know the Cat. numbers) had a real-world BC only equal to my 155 FLAT-BASE! 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. Mr. Childs extreme 'tipping' experiment may have provided empirical evidence that a SHARP point is undesirable. RGRG, as I remember, McCoy later retracted that statement. I'm not familiar with the particular test by Henry Childs you're referring to, but I do remember he had one tip -- he was making his own tips and inserting them like the A-max & Nosler tips -- where it turned out the problem wasn't so much the sharpness of the point, but that particular aluminum tip was loading the bullet at the ogive/shank junction, which is weak.. . . 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.
In spite of Jim Hardy's observations, and I listen to him as a serious shooter, more work is needed on all this.
Out of curiosity, what would the increase in BC be if, for example, you just changed the meplat diameter in the 108 BIB from (.052 is it?) to .010? All that ignoring for a moment that such a re-point would slightly change the ogive radius at the point, what's the theoretical increase in BC?
Charles
Charles:
Of course, I have been thinking about Ferris Pindell's passing this week, and that has brought back many memories bout the meplat closing die. With those memories, I recall more than a few times when I would get in touch with a WORLD CLASS prone or F-Class shooter and offer to close their meplats for free just so they could see the difference. I would often get a reply from some very famous shooters to the extent that "I have been pretty successful doing what I am doing" or "I don't have the time to experiment" or "beat me with closed meplats and I might think about it". I smile when I now know for a fact, with many saying so in print, that ALL of these shoters now shoot closed meplats. I never got a "you told me so" response from any of them.
I remember being at a competition where a very successful shooter who would not touch closed meplats lost a huge competition to a closed meplat shooter by one X (not saying F-Class or prone which shoot together in most matches). In eating dinner with shooters that evening, I could hear in a low voice: "With all the expense of this competition, and all my hard work, I would have paid anything for one more on-the-line X today." He could have had it for FREE as I had offered
As Ferris has said: ". . . accuracy is the result of a multitude of tremendous trifles."
Jim
Of course, I have been thinking about Ferris Pindell's passing this week, and that has brought back many memories bout the meplat closing die. With those memories, I recall more than a few times when I would get in touch with a WORLD CLASS prone or F-Class shooter and offer to close their meplats for free just so they could see the difference. I would often get a reply from some very famous shooters to the extent that "I have been pretty successful doing what I am doing" or "I don't have the time to experiment" or "beat me with closed meplats and I might think about it". I smile when I now know for a fact, with many saying so in print, that ALL of these shoters now shoot closed meplats. I never got a "you told me so" response from any of them.
I remember being at a competition where a very successful shooter who would not touch closed meplats lost a huge competition to a closed meplat shooter by one X (not saying F-Class or prone which shoot together in most matches). In eating dinner with shooters that evening, I could hear in a low voice: "With all the expense of this competition, and all my hard work, I would have paid anything for one more on-the-line X today." He could have had it for FREE as I had offered
As Ferris has said: ". . . accuracy is the result of a multitude of tremendous trifles."
Jim
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Now Jim, you know, as I know, that the world churns. Had he taken you up on your offer, just as he broke the shot, a horsefly would have bitten him on the finger, and a gust of wind would blow the bullet even further off. But it wouldn't have mattered, because just at that moment, a tornado would set down and take him & his rifle to the top of a tree.. . . "With all the expense of this competition, and all my hard work, I would have paid anything for one more on-the-line X today." He could have had it for FREE as I had offered
To explain why I haven't run the numbers myself: Back when I started our business, I worked 12-14 hours a day. I wouldn't have a computer at home, since I spent all day & half the night at work with them. But my wife did. Now, I'm a PC guy, she's Mac. So when I got Art Pejsa's ballistics program, I ordered it for the Mac, the "home" machine. When I finally got a computer of my own at home, it was the familiar (to me) Windows platform. I called Mr. Pejsa. No, he says, if you want a Windows version, reorder & repay.
What the hell, my wife's nice, I'll just use her Mac. But now she got a new one. It doesn't have a floppy drive, so I can't load the software. And just now, she's out lifting up the car & changing the tire . . .
Why do you think I've been trying to get someone else to run the numbers on a ballistics program? But I'll bite the bullet (so to speak) and get her to (somehow) load the software from the floppy. Then we'll see how much increase in BC it takes to reduce drop by 1.8 minutes at 1,000 yards when a 6mm 106 is launched at 3,000 fps.
* * *
I keep telling you that I DO close and uniform meplats. I've even gotten John Whidden's die, which you recommend. I'll allow it's not as nice as the Pindell lathe you got, but it works.
In fact, I was one of the guys who had to duck the flung garbage for advocating trimming meplats for 200 yard point-blank group shooting -- the variation in drift from a .020 ES in drag can be significant at 200, when you're trying to shoot small. Jeeze, you'd have thought I was recommending a boob job for Lauren Bacall.
What I object to is giving point & trim as a blanket answer, esp. for a guy having trouble with group size at 400 yards.
You want the 106 CR to strike 18 inches higher at 1,000? One way's to rechamber to 6 Ackley . . .
I have some experimental 187s from Randy. I'm suppose to keep it mum. If you can put 2+2 together with his other newer offerings, you can figure out what someone *might* do to the 187s, I'll neither confirm or deny. They hit significantly higher that the old 187s. But when I close the point, the further gain so small to be in the noise. What can I say?
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Damon
Guest
Charles,
I've just written my own point mass calculator (basically, just as described in McCoy's book). I've been thinking about what to do with it and other similar projects to undertake.
What sort of numbers do you need crunched? I can set it up to do all sorts of things. (The nice part being that I can script it to run over and over again. You can get creative when you don't have to keep clicking and recording data). Since I wrote it, I can do pretty much anything with it.
I've just written my own point mass calculator (basically, just as described in McCoy's book). I've been thinking about what to do with it and other similar projects to undertake.
What sort of numbers do you need crunched? I can set it up to do all sorts of things. (The nice part being that I can script it to run over and over again. You can get creative when you don't have to keep clicking and recording data). Since I wrote it, I can do pretty much anything with it.
Hey Damon,
Well, the first thing would be to quantify the observed phenomena -- Jason Baney shooting repointed 106 Clinch River bullets at 1,000 yards from a Dasher. His bullet strike was 18 inches higher with the repointed bullets. Lets say MV was around 3,000 fps, and the raw bullet had a real-world BC of .520 -- the Clinch River's are a high-number tangent ogive, with a very good (even) meplat of about .050
So how much increase in BC would it take, with no other changes, to get that bullet strike of 18 inches higher?
Or, as I mentioned earlier, if you took a bullet using the JBM calculator, also based on Bob McCoys work, what happens as you change the only the meplat diameter -- say a .30 with an existing diameter of .062 down to about .025? That's about as far as I can go, but I'd imagine Jim Hardy with his Pindell system, might be able to get as low as .015.
And I don't know enough to know if the small distance the repointing affects -- a secant in the Whidden die -- changes the characteristic of the bullet -- see Bryan Litz piece at
http://www.appliedballisticsllc.com/bulletdesign.html
especially the section On tangent vs secant ogive nose design:, where "optimal shape" is a mixture of tangent and secant ogives. Repointing affects only about 1/8-inch of the bullet's length. So, for example, with the BIB, the general shape is a 10-caliber tangent ogive, about .725 long beyond the shank. Closing the meplats in a Whidden die changes the last .110 to a secant of unknown radius, but not great -- maybe 7 calibers? Can that explain any of this?
Etc.
Well, the first thing would be to quantify the observed phenomena -- Jason Baney shooting repointed 106 Clinch River bullets at 1,000 yards from a Dasher. His bullet strike was 18 inches higher with the repointed bullets. Lets say MV was around 3,000 fps, and the raw bullet had a real-world BC of .520 -- the Clinch River's are a high-number tangent ogive, with a very good (even) meplat of about .050
So how much increase in BC would it take, with no other changes, to get that bullet strike of 18 inches higher?
Or, as I mentioned earlier, if you took a bullet using the JBM calculator, also based on Bob McCoys work, what happens as you change the only the meplat diameter -- say a .30 with an existing diameter of .062 down to about .025? That's about as far as I can go, but I'd imagine Jim Hardy with his Pindell system, might be able to get as low as .015.
And I don't know enough to know if the small distance the repointing affects -- a secant in the Whidden die -- changes the characteristic of the bullet -- see Bryan Litz piece at
http://www.appliedballisticsllc.com/bulletdesign.html
especially the section On tangent vs secant ogive nose design:, where "optimal shape" is a mixture of tangent and secant ogives. Repointing affects only about 1/8-inch of the bullet's length. So, for example, with the BIB, the general shape is a 10-caliber tangent ogive, about .725 long beyond the shank. Closing the meplats in a Whidden die changes the last .110 to a secant of unknown radius, but not great -- maybe 7 calibers? Can that explain any of this?
Etc.
Charles, Charles, Charles. You don't need no stink'n computer program. Just send me the 6mm 106 grain Clinch River VLDs. Send me 100 so you have enough to run the test any way you want. Post the results here. PLEASE.
Keep us informed on the expeerimental 187 BIBs as everything Mr. R makes is top shelf.
Thanks,
Jim
Keep us informed on the expeerimental 187 BIBs as everything Mr. R makes is top shelf.
Thanks,
Jim
R.G. Robinett
"That'll never work."
Charles, hypothetically, this - decreasing the meplat diameter from 0.05, to 0.01' - would increase the CALCULATED BC (real-world is always less) of the 108 BIB BT by about 0.040: from 0.542 to 0.583. Removing the BT, but using the 0.01 meplat, reduces the calculation to BC to .556, while the calculated BC for the actual meplat diameter (0.052) and a FB results in a BC of .514. BTW, the stubby BT on the BIB 108s/95s, provided > 98% of the BC potential - either longer BT are over-rated, or, the math is simply wrong!
For example, opting for a 10 degree, 0.20" long BT, with the 0.01" diameter meplat, produces a calculated BC of .587: a mere 1% increase over the first model ( above - .583/.587) - who can shoot THAT?!? The relativity holds up for the actual bullets also! Oh, and, for those who don't know me, I don't make this stuff up - these calculations are from the Tioga Engineering (the late Bill Davis) program, which, used in conjunction with the McCoy based programs at JBM BALLISTICS, has resulted in some decent real-world results. The Tioga and McCoy results are alway very close . . . well, unless I enter bad data! A 0.010" knock-out pin would need some SPINE! RG
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Damon
Guest
Charles, my results show you'd need to go from a .520 to about a .575 to get 18" at 1000 yards. Seems like quite a difference.
As for the impact the point diameter has on BC, I have an idea I want to try that may or may not shed any useful light on the subject.
As for the impact the point diameter has on BC, I have an idea I want to try that may or may not shed any useful light on the subject.
OK, Damon's number of an needed increase in BC from .520 to .575 sort of, kind of, agrees with RG's calculation (.583) of what might be available. Except, RG started with a higher BC number -- the increase with the BIBs was .040, less that the .055 Damon calculated as needed.
Before everyone gets all hot & sweaty, remember too that RG said this was the theoretical improvement with a .01 meplat, and real world would be less.
You bet.
In part because you'll not likely get a .01 meplat diameter in the real world. For those that don't know, AS I REMEMBER, Jim Hardy's Ferris Pindell built system includes a precision lathe that lets him remove some metal at the point of the bullet. That will let him close the points more that those of us with only a die. Correct me if I'm wrong, Jim. And just how small a point can you get?
And Jim, you know me. I gotta know why whenever possible. Not that I wont take results only, but the "why's" sometimes lead to even more useful knowledge, and I suspect that may be the case here. Been wrong a lot, too.
If I send you bullets, it would be the 108 BIBs. I've only got 200 of the old CRs left, but RG's getting me 1,000 of his 108-BT in due course. You up for them?
Charles
Before everyone gets all hot & sweaty, remember too that RG said this was the theoretical improvement with a .01 meplat, and real world would be less.
You bet.
In part because you'll not likely get a .01 meplat diameter in the real world. For those that don't know, AS I REMEMBER, Jim Hardy's Ferris Pindell built system includes a precision lathe that lets him remove some metal at the point of the bullet. That will let him close the points more that those of us with only a die. Correct me if I'm wrong, Jim. And just how small a point can you get?
And Jim, you know me. I gotta know why whenever possible. Not that I wont take results only, but the "why's" sometimes lead to even more useful knowledge, and I suspect that may be the case here. Been wrong a lot, too.
If I send you bullets, it would be the 108 BIBs. I've only got 200 of the old CRs left, but RG's getting me 1,000 of his 108-BT in due course. You up for them?
Charles
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Damon
Guest
OK one more bit of math. Bryan Litz took the data he measured in his book and did a curve fit to try to figure out a predictive model for BC's. I took that equation, and recalculated the G7 BC for a JLK 105 VLD (he's got those in his book). The predicted G7 BC for the JLK comes out to .271 (vs. .267 measured). I then reduced the meplat diameter from .058 to .025. The new calculated BC was .334! If that were real, it would result in a POI 35" higher at 1000 yards.
Now, there is a lot wrong with this method. Bryan's magic equation (on p 296 of his book) is simply a curve fit through all of his data and therefore purely empirical. Also, you can't actually make the bullet I input. You'd have to change the ogive radius or ogive length to make it geometrically possible. And since his data is pretty much all bullets with one ogive radius, you might wonder if it's still good with the two-radius ogive created by pointing (the original ogive radius, plus the bit at the end which gets a smaller radius from the pointing operation).
Frankly, it surprises me that such a small change has any impact at all (not that I have any experience to make my gut instinct worth anything on this). But this is really, really back of the envelope stuff. Still, enough to make me wonder if there shouldn't be more effort put into testing these things.
Now, there is a lot wrong with this method. Bryan's magic equation (on p 296 of his book) is simply a curve fit through all of his data and therefore purely empirical. Also, you can't actually make the bullet I input. You'd have to change the ogive radius or ogive length to make it geometrically possible. And since his data is pretty much all bullets with one ogive radius, you might wonder if it's still good with the two-radius ogive created by pointing (the original ogive radius, plus the bit at the end which gets a smaller radius from the pointing operation).
Frankly, it surprises me that such a small change has any impact at all (not that I have any experience to make my gut instinct worth anything on this). But this is really, really back of the envelope stuff. Still, enough to make me wonder if there shouldn't be more effort put into testing these things.
D
Damon
Guest
This got me thinking, so I reread some sections of a few ballistics books. Specifically interesting is the section in McCoy's book on Drag. Although he's light on detail (and frustratingly references BRL reports that I have no idea how to get), it appears that there is likely an optimal meplat size (he suggests 0.1-0.15 calibers). Going sharper than that should raise drag. (Note that Litz's equation will not catch this effect - according to it, smaller is always better, at least in the realistic area).
An interesting test would be to load up several samples of the same ammo, but with differing pointing. Say, .015, .025, .035, .45, .055. Then measure the vertical difference between groups at 1000 yards. If anything showed up there, you'd know you have something. Plus you'd know where the optimum is.
An interesting test would be to load up several samples of the same ammo, but with differing pointing. Say, .015, .025, .035, .45, .055. Then measure the vertical difference between groups at 1000 yards. If anything showed up there, you'd know you have something. Plus you'd know where the optimum is.
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As I said in an earlier post, I *believe* McCoy later recanted that. Maybe Bryan would know?
In any case, I believe it false. For example, 0.1 of a .308 would be .030 as optimum meplat diameter. I've gone smaller than that and the shots printed much higher than standard (with some bullets). Though in truth, I've never done a quantitative test comparing, say, .030 with .025 with .040, etc. Maybe someone has?
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Damon
Guest
Even if he did not recant it, I'm not sure what was written was universally applicable. He just didn't give enough detail to really dig into it. What I'd give to go digging around in those old BRL files!
I think this is as far as we're likely to get with textbook math (at least by me - I have no better way of predicting BC than Bryan's regression (which is surprisingly good, at least when you're talking about "normal" bullets). Looks like testing is worth while if these numbers we're throwing about are even close to correct.
I think this is as far as we're likely to get with textbook math (at least by me - I have no better way of predicting BC than Bryan's regression (which is surprisingly good, at least when you're talking about "normal" bullets). Looks like testing is worth while if these numbers we're throwing about are even close to correct.
Charles:
Yes, I know how to get the meplats closed like darts on nice 6mm VLDs. However, on the 6mm CR 106s I sent to Jason -- as well as the ones I tested in the prone at Camp Butner at 1000 -- I did NOTHING but close the meplats. Keep in mind that I asked Jason to test 58 of thes bullets (actually culls from my sorting). I know I mentioned that I liked his testing procedure at the PA Club, but I gave him no other info -- except that I wanted nothing from him in any way beyond his final analysis.
The load I shot at Butner was the same load and gun used by John Whidden to shoot 26 straight Xs at his 1000 yd home range in April 2006 -- just destroyed the spotter in 7 minutes of wind with let offs to 4 minutes (shot from the prone with my NF scope and Gilkes-Ross prone rifle chambered in 6BR). This is what got his attention and put him on the road to developing his die.
I don't know how to find this old thread with the new format. Maybe it is on 6mmBR.com as well but I don't know. Again, if you know how to find the old thread and Jason's posts and pictures of his testing, that would be food for thought.
As to the 108 BIBs, I have never closed the meplats on these nice Tangent ogives. My experience tells me I can improve the BC and the consistency of the BC, but I don't know how much vertical difference there will be. I KNOW it will not compare with a nice 6mm VLD. But again, the "challenge" so to speak, is whether this can be done with a 6mm 106 CR -- it HAS been done MANY times. If we can get a box of 100, you can end all speculation once and for all. Then used the computer programs to figure out the WHY after you have found the bottom line -- 17" to 18" vertical differnce at 1000. That is the "ultimate" test. 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.
I hope we can find a way to do this.
Hope to see you soon at Butner if I can get up that way for awhile. Give my best to Joel as well.
Jim
Yes, I know how to get the meplats closed like darts on nice 6mm VLDs. However, on the 6mm CR 106s I sent to Jason -- as well as the ones I tested in the prone at Camp Butner at 1000 -- I did NOTHING but close the meplats. Keep in mind that I asked Jason to test 58 of thes bullets (actually culls from my sorting). I know I mentioned that I liked his testing procedure at the PA Club, but I gave him no other info -- except that I wanted nothing from him in any way beyond his final analysis.
The load I shot at Butner was the same load and gun used by John Whidden to shoot 26 straight Xs at his 1000 yd home range in April 2006 -- just destroyed the spotter in 7 minutes of wind with let offs to 4 minutes (shot from the prone with my NF scope and Gilkes-Ross prone rifle chambered in 6BR). This is what got his attention and put him on the road to developing his die.
I don't know how to find this old thread with the new format. Maybe it is on 6mmBR.com as well but I don't know. Again, if you know how to find the old thread and Jason's posts and pictures of his testing, that would be food for thought.
As to the 108 BIBs, I have never closed the meplats on these nice Tangent ogives. My experience tells me I can improve the BC and the consistency of the BC, but I don't know how much vertical difference there will be. I KNOW it will not compare with a nice 6mm VLD. But again, the "challenge" so to speak, is whether this can be done with a 6mm 106 CR -- it HAS been done MANY times. If we can get a box of 100, you can end all speculation once and for all. Then used the computer programs to figure out the WHY after you have found the bottom line -- 17" to 18" vertical differnce at 1000. That is the "ultimate" test. 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.
I hope we can find a way to do this.
Hope to see you soon at Butner if I can get up that way for awhile. Give my best to Joel as well.
Jim