Hornady ELD-X bullets
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Thanks Bryan, It looks like they've already addressed those possibilities here - http://www.hornady.com/assets/files/FAQ-ELD-HeatShield.pdf
Thanks for posting that Q&A paper. It directly addresses all of the points in my post.
There is one question that isn't addressed very well, and that is the issue of the drag jumping so high, so fast.
Consider Figure 1 in the link (http://www.hornady.com/assets/files/FAQ-ELD-HeatShield.pdf) The drag of the old tip is immediately higher than the heat shield tip. Hornady explains this is due to the radar picking up the track 40-50 yards downrange. The plot shows that by this point (40-50 yards) the drag is already different by about 5%. Assuming the tips are the same shape, this implies that the old tip melted enough in 40-50 yards (0.06 seconds) to already be different by 5%.
By the time the bullet slows to ~Mach1.85 (~2065 fps) the bullet is about 400 yards downrange and the drag is now different by more than 10%. At this point the bullet has flown for only 0.52 seconds, and the old tip has already deformed enough to increase it's drag by more than 10%.
By my rough calculations, a tip would have to increase in diameter by about 0.050" to make 10% more drag if that's the only thing going on. Measuring one of the old Hornady tips from an SST bullet, the tip is about 0.040" in diameter, and the base of the plastic tip is like 0.100". So in order for this plastic to produce 10% more overall drag for the bullet, the tip would have to melt from 0.040" to ~0.090", when the metal part is 0.100". In other words, it would have to nearly melt entirely off, all in 0.52 seconds.
At this point, the mad scientist part of me reached for a lighter
Some quick internet research indicates that a standard butane Bic lighter has a flame temperature of 3000-4000 degrees F. So I light up the tip of the Hornady SST bullet I just measured. Holding the plastic tip in the hottest part (top) of the flame, it took about 5 seconds before any noticeable deformation began to occur. According to Hornady's original research paper (http://www.hornady.com/assets/files/resources/ELD-X_ELD-Match_Technical_Details.pdf) the stagnation temperature on the bullet tips is under 1000 degrees F for a velocity of 3000 fps.
So, How can the tips nearly melt completely off in 0.52 seconds at in-flight temperature of under 1000 degrees F, when it takes a bic lighter more than 5 seconds to begin melting the tip at 3000 degrees F?
There is the matter of aerodynamic force being applied to the tip, which is absent in my lighter test. Based on the bullet losing about 150 fps in the first 100 yards (0.119 seconds), we can calculate the average force to be:
F=M*a
F=(140/7000/32.2)*(150/0.119)
F=0.78 pounds
So there's roughly 0.78 pounds of aerodynamic drag (force) acting to slow the bullet over the first 100 yards on average. Only a fraction of that force is applied to the actual tip. Could that small amount of force, combined with the heat, result in the tips deforming in such a short time?
Going back to figure 1, we see that the difference in drag is maximized at around Mach 1.85 (~2065 fps), but then something strange happens. The drag of the old and new tip bullets converges back together again. By the time the bullet has slowed to Mach 1.25 (~1395 fps, somewhere around 950 yards), the drag of the two bullets is nearly the same, with the new and old tipped bullets matching to within about 2%.
How is it that a tip melts enough to produce more than 10% difference in drag by 400 yards, can 'heal' itself further downrange and fly with nearly the same drag as a 'non-melted' tip by 950 yards?
Several places in Hornady's Q&A document, they mention that all of the old tips melt (as well as all other brands). But the heat shield tips are only used on long range bullets because the effect only matters when you're shooting past 400 yards. I don't see this going over well with all the guys who've been shooting Amax bullets at long range. Hornady is now saying that yesterdays long range match bullet (the Amax) is now limited to 400 yards, and you need the new ELD-X bullets to hit anything past 400 yards. That's simply not consistent with the observations many have made shooting long range with Amax bullets.
The questions about tips melting are interesting, and still not entirely settled for me. Not having been present for the testing, I don't have any strong alternate theories to explain the drag data their publishing. I'll reiterate the positives of the ELD-X line as: heavy for caliber bullets intended for long range, and represented with G7 BC's which appear to be accurate. Introducing more options in this class is a good thing, regardless of the questions about plastic tips.
-Bryan
There is one question that isn't addressed very well, and that is the issue of the drag jumping so high, so fast.
Consider Figure 1 in the link (http://www.hornady.com/assets/files/FAQ-ELD-HeatShield.pdf) The drag of the old tip is immediately higher than the heat shield tip. Hornady explains this is due to the radar picking up the track 40-50 yards downrange. The plot shows that by this point (40-50 yards) the drag is already different by about 5%. Assuming the tips are the same shape, this implies that the old tip melted enough in 40-50 yards (0.06 seconds) to already be different by 5%.
By the time the bullet slows to ~Mach1.85 (~2065 fps) the bullet is about 400 yards downrange and the drag is now different by more than 10%. At this point the bullet has flown for only 0.52 seconds, and the old tip has already deformed enough to increase it's drag by more than 10%.
By my rough calculations, a tip would have to increase in diameter by about 0.050" to make 10% more drag if that's the only thing going on. Measuring one of the old Hornady tips from an SST bullet, the tip is about 0.040" in diameter, and the base of the plastic tip is like 0.100". So in order for this plastic to produce 10% more overall drag for the bullet, the tip would have to melt from 0.040" to ~0.090", when the metal part is 0.100". In other words, it would have to nearly melt entirely off, all in 0.52 seconds.
At this point, the mad scientist part of me reached for a lighter
Some quick internet research indicates that a standard butane Bic lighter has a flame temperature of 3000-4000 degrees F. So I light up the tip of the Hornady SST bullet I just measured. Holding the plastic tip in the hottest part (top) of the flame, it took about 5 seconds before any noticeable deformation began to occur. According to Hornady's original research paper (http://www.hornady.com/assets/files/resources/ELD-X_ELD-Match_Technical_Details.pdf) the stagnation temperature on the bullet tips is under 1000 degrees F for a velocity of 3000 fps.So, How can the tips nearly melt completely off in 0.52 seconds at in-flight temperature of under 1000 degrees F, when it takes a bic lighter more than 5 seconds to begin melting the tip at 3000 degrees F?
There is the matter of aerodynamic force being applied to the tip, which is absent in my lighter test. Based on the bullet losing about 150 fps in the first 100 yards (0.119 seconds), we can calculate the average force to be:
F=M*a
F=(140/7000/32.2)*(150/0.119)
F=0.78 pounds
So there's roughly 0.78 pounds of aerodynamic drag (force) acting to slow the bullet over the first 100 yards on average. Only a fraction of that force is applied to the actual tip. Could that small amount of force, combined with the heat, result in the tips deforming in such a short time?
Going back to figure 1, we see that the difference in drag is maximized at around Mach 1.85 (~2065 fps), but then something strange happens. The drag of the old and new tip bullets converges back together again. By the time the bullet has slowed to Mach 1.25 (~1395 fps, somewhere around 950 yards), the drag of the two bullets is nearly the same, with the new and old tipped bullets matching to within about 2%.
How is it that a tip melts enough to produce more than 10% difference in drag by 400 yards, can 'heal' itself further downrange and fly with nearly the same drag as a 'non-melted' tip by 950 yards?
Several places in Hornady's Q&A document, they mention that all of the old tips melt (as well as all other brands). But the heat shield tips are only used on long range bullets because the effect only matters when you're shooting past 400 yards. I don't see this going over well with all the guys who've been shooting Amax bullets at long range. Hornady is now saying that yesterdays long range match bullet (the Amax) is now limited to 400 yards, and you need the new ELD-X bullets to hit anything past 400 yards. That's simply not consistent with the observations many have made shooting long range with Amax bullets.
The questions about tips melting are interesting, and still not entirely settled for me. Not having been present for the testing, I don't have any strong alternate theories to explain the drag data their publishing. I'll reiterate the positives of the ELD-X line as: heavy for caliber bullets intended for long range, and represented with G7 BC's which appear to be accurate. Introducing more options in this class is a good thing, regardless of the questions about plastic tips.
-Bryan
Thanks for posting that Q&A paper. It directly addresses all of the points in my post.
There is one question that isn't addressed very well, and that is the issue of the drag jumping so high, so fast.
Consider Figure 1 in the link (http://www.hornady.com/assets/files/FAQ-ELD-HeatShield.pdf) The drag of the old tip is immediately higher than the heat shield tip. Hornady explains this is due to the radar picking up the track 40-50 yards downrange. The plot shows that by this point (40-50 yards) the drag is already different by about 5%. Assuming the tips are the same shape, this implies that the old tip melted enough in 40-50 yards (0.06 seconds) to already be different by 5%.
By the time the bullet slows to ~Mach1.85 (~2065 fps) the bullet is about 400 yards downrange and the drag is now different by more than 10%. At this point the bullet has flown for only 0.52 seconds, and the old tip has already deformed enough to increase it's drag by more than 10%.
By my rough calculations, a tip would have to increase in diameter by about 0.050" to make 10% more drag if that's the only thing going on. Measuring one of the old Hornady tips from an SST bullet, the tip is about 0.040" in diameter, and the base of the plastic tip is like 0.100". So in order for this plastic to produce 10% more overall drag for the bullet, the tip would have to melt from 0.040" to ~0.090", when the metal part is 0.100". In other words, it would have to nearly melt entirely off, all in 0.52 seconds.
At this point, the mad scientist part of me reached for a lighter
So, How can the tips nearly melt completely off in 0.52 seconds at in-flight temperature of under 1000 degrees F, when it takes a bic lighter more than 5 seconds to begin melting the tip at 3000 degrees F?
There is the matter of aerodynamic force being applied to the tip, which is absent in my lighter test. Based on the bullet losing about 150 fps in the first 100 yards (0.119 seconds), we can calculate the average force to be:
F=M*a
F=(140/7000/32.2)*(150/0.119)
F=0.78 pounds
So there's roughly 0.78 pounds of aerodynamic drag (force) acting to slow the bullet over the first 100 yards on average. Only a fraction of that force is applied to the actual tip. Could that small amount of force, combined with the heat, result in the tips deforming in such a short time?
Going back to figure 1, we see that the difference in drag is maximized at around Mach 1.85 (~2065 fps), but then something strange happens. The drag of the old and new tip bullets converges back together again. By the time the bullet has slowed to Mach 1.25 (~1395 fps, somewhere around 950 yards), the drag of the two bullets is nearly the same, with the new and old tipped bullets matching to within about 2%.
How is it that a tip melts enough to produce more than 10% difference in drag by 400 yards, can 'heal' itself further downrange and fly with nearly the same drag as a 'non-melted' tip by 950 yards?
Several places in Hornady's Q&A document, they mention that all of the old tips melt (as well as all other brands). But the heat shield tips are only used on long range bullets because the effect only matters when you're shooting past 400 yards. I don't see this going over well with all the guys who've been shooting Amax bullets at long range. Hornady is now saying that yesterdays long range match bullet (the Amax) is now limited to 400 yards, and you need the new ELD-X bullets to hit anything past 400 yards. That's simply not consistent with the observations many have made shooting long range with Amax bullets.
The questions about tips melting are interesting, and still not entirely settled for me. Not having been present for the testing, I don't have any strong alternate theories to explain the drag data their publishing. I'll reiterate the positives of the ELD-X line as: heavy for caliber bullets intended for long range, and represented with G7 BC's which appear to be accurate. Introducing more options in this class is a good thing, regardless of the questions about plastic tips.
-Bryan
Bryan, If I look at my McCoy book on page 71 where he has the meplat chart, I think you're over estimating the tip size change a lot. His graph only goes up to mach 1.8 so I would guess that at 2.5 the change of Cd vs meplat diameter gets even worse. At mach 1.8 your only talking about .030" of meplat change for a .264" diameter bullet to get a 10% increase in drag. It's probably less than that at Mach 2.5.
No offence, but radar data of actual aerodynamic bullet performance is more compelling than Bic lighter data.
If you look at those meplat curves you can also see that the meplat diameter has less and less effect on the drag as the projectile slows down to the point that at 1.3 it almost doesn't matter, at least up to the limit of the graph at .3 calibers. I think they even kind of said something like that in the FAQ.
As far as your force calculation goes you need to convert that to pressure. Concentrate .78 lbs. of force on .040" diameter of hot plastic and I'd be willing to bet it will deform.
Lastly, the way I read their FAQ and white paper they aren't saying you can't hit anything with the current AMAX. They are saying that if a BC determined over short range is used to calculate trajectories that you will have a lot of error at long range. That's why in the white paper they put the 800 yards BC's for the old AMAX. I think what they are trying to say is the new tip is a better mouse trap.
Bullseye,
You make some good points. I'm not trying to invalidate Hornady's work with a bic lighter, but some of their explanations are difficult to accept in light of some common sense observations.
Bic lighters aside, Amax bullets and other tipped bullets have been flying well at long range for many years. By flying well I mean:
Flying with BC's that are consistent with the shape of non-deformed tips, and
Flying with trajectories that are predictable with these BC's.
All of a sudden, a discovery is claimed which suggests that trajectories are not predictable, and BC's are lower than they should be, which goes against years of direct observation by many shooters and my own measurements.
In order to accept the claim of 'melting tips' as reality, we have to:
A) accept that the testing and doppler radar data that Hornady is presenting is accurate (free of excessive measurement error). This is the part that is actually contrary to common observation.
B) accept that the melting tip theory explains why the data indicates performance that's different from what we know it to be.
I've been measuring BC's for bullets for many years. Plastic tipped bullets of all calibers have very uniform BC's, which are consistent with the mass, caliber and un-deformed shape of the bullet. For me personally, it will take more evidence to believe this data, and the conclusions being drawn from it.
To be clear, I'm not saying they're wrong, but there are good questions to ask.
-Bryan
You make some good points. I'm not trying to invalidate Hornady's work with a bic lighter, but some of their explanations are difficult to accept in light of some common sense observations.
Bic lighters aside, Amax bullets and other tipped bullets have been flying well at long range for many years. By flying well I mean:
Flying with BC's that are consistent with the shape of non-deformed tips, and
Flying with trajectories that are predictable with these BC's.
All of a sudden, a discovery is claimed which suggests that trajectories are not predictable, and BC's are lower than they should be, which goes against years of direct observation by many shooters and my own measurements.
In order to accept the claim of 'melting tips' as reality, we have to:
A) accept that the testing and doppler radar data that Hornady is presenting is accurate (free of excessive measurement error). This is the part that is actually contrary to common observation.
B) accept that the melting tip theory explains why the data indicates performance that's different from what we know it to be.
I've been measuring BC's for bullets for many years. Plastic tipped bullets of all calibers have very uniform BC's, which are consistent with the mass, caliber and un-deformed shape of the bullet. For me personally, it will take more evidence to believe this data, and the conclusions being drawn from it.
To be clear, I'm not saying they're wrong, but there are good questions to ask.
-Bryan
jimbires
Well-Known Member
thought you guys might be interested in nosler bullets FAQ on plastic tips .
Nosler FAQ - What happens to the polymer tip in the bullet after being fired from the rifle?
Nosler FAQ - What happens to the polymer tip in the bullet after being fired from the rifle?
Barrelnut
Well-Known Member
Ah, if life were only that easy! LOL
Rich Coyle
Well-Known Member
Interesting info. How did they arrive at their conclusion?
Barrelnut
Well-Known Member
They don't say. It is from the Nosler FAQ page. It is rev 1, dated 10/08/2014, and has been viewed 23,000 plus times though. I am sure it would have support from their Engineering dept. or they would not have published it.
Would suspect, one of these days, Nosler will have to comment on Hornady's allegation of widespread tip meltdown...
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- Aug 30, 2006
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- 283
Has anyone measured the functional BC of the 7mm 175 grain NLAB though it entire terminally effective velocity? Hornady estimates a MUCH lower BC (based on Radar measured data) for the NLAB than is advertised. Perhaps Bryan can share his testing results for this bullet.
7mmShooter
Well-Known Member
If I remember correctly it averaged a .331 G7 (+/- a couple points) in Bryan's testing of the 175 LRAB.
Michael Eichele
Well-Known Member
How far from the muzzle do you collect your last data point for purposes of calculating your published BC values? When testing high BC bullets likely to be used long range.
