Applied Ballistics vs Hornady BCs

[wind gypsy]

There's a fair bit of discrepancy between AB's listed BCs and Hornady's for the ELDm line and it's not just a consistent % difference. For example, I always assumed the 75 ELDm had a better form factor than the 80 because the Hornady listed BC is very close. AB's #'s say the opposite.

	Hornady G7	AB G7
75​	0.235​	0.238​
80​	0.244​	0.258​
88​	0.274​	0.264​

Based on AB #s, the 80 ELDm looks really good for a balance of possible velocity and BC while Hornady's #'s make the 75 and 88 more attractive. When the 3 bullets are placed next to each other, the eye test indicates the BCs should align more with Hornady's BC progression - the 80 looks like just bearing surface added to a 75 at best, maybe even a shorter nose. The 88 looks like nose and boattail length added to an 80.

I'm curious on other's thoughts. Is this possibly just lot to lot variance on bullets that were tested?

There's a similar thing going on with the .257 134 grain and .264 140 grain - Hornady lists them at basically the same BC which to me suggests there would be very little benefit to the .25 creed vs 6.5 creed with these two bullets as the velocity benefit of the 134 should be small. However, AB #'s significantly favor the 134 so having a velocity, BC, and recoil advantage would give it the bigger edge.

I use AB custom curves for solutions rather than BC #s and realize this is mostly just noise in any of my real life applications but I found it interesting for discussion.

 

[SouthPaw]

I noticed this, too. AB claims a G7 form factor of .882 for the 80 which is crazy for a 22cal. If their numbers are correct, that's a 2% increase in G7 BC for a 10% increase in bullet weight going from 80 to 88.

It'll be interesting to see where the 80g ELDx BC ends up.

 

[hereinaz]

Use the custom curve. It is an actual “map” of the bullet over time.

BC is based on the form factor or model, not the actual shape of the bullet. It is close but it isn’t perfect. And, BC is changing depending on what yardage it is measured.

Hornady uses a yardage and I think AB uses the best BC as posted below. They end up with a different BC for philosophical reasons which BC to publish.

If AB gives a BC I would trust that to be the best.

 

[hereinaz]

Hornady used to use the 800 yard BC but switched to the 200 yard because consumers didn’t understand the difference on boxes.

Ballistic Coefficient - Hornady Manufacturing, Inc

A-Tip®, ELD® Match, and ELD-X® Ballistic Coefficient Values Hornady originally published “800 yard”* average Ballistic Coefficient (BC) values for ELD-X and ELD Match bullets. This was done to provide the most usable BC from a trajectory prediction st...

www.hornady.com

 

[hereinaz]

AB explainer on BC here.

Here is a link to AB education page. I pulled this from their page.

The bullets drag coefficient as well as it’s G1 and G7 form factors and BC’s are tabulated in 500 fps increments from 3000 down to 1500 fps. This is useful for determining which standard (G1 or G7) is a better fit for the particular bullet. The BC which shows the least amount of variation over the velocity range is the appropriate BC to use. Typically for boat tail bullets, the G7 standard is a better representation.​

I didn’t find it, but I think AB chooses the best BC to use for each bullet, not the BC at an arbitrary yardage like Hornady.

That would explain why BC might vary as it does.

 

[hereinaz]

I laugh at the last paragraph in the Hornady screen shot, because AB has been the leader pushing first to use the G7 and publishing useful BC information.

I am sure Hornady is pushing for realistic BC among manufacturers, they tried to use the 800 yard but had to switch to the 200 yard because it wasn’t easy to explain the difference on a box of bullets when uneducated consumers compare.

 

[ID_Matt]

The 180 ELDM is another one that baffles me. HUGE difference between hornady suggested BC and AB BC

 

[hereinaz]

Comparing the numbers, elongating the bullet from 75 to 80 gets more gain % wise in BC because it pushes the form factor by adding weight into the stretch of the pointy part.

There are diminishing returns from 80 to 88 because most all that is happening with the weight is elongating the body of bullet.

 

[wind gypsy]

Comparing the numbers, elongating the bullet from 75 to 80 gets more gain % wise in BC because it pushes the form factor by adding weight into the stretch of the pointy part.

There are diminishing returns from 80 to 88 because most all that is happening with the weight is elongating the body of bullet.

The AB #'s would make sense if what you said was true but it appears that the changes are the opposite of what you're saying.

From 75-80 it looks like primary length is gained in bearing surface (and aligns with hornady listing the same min twist for both). From 80-88 it looks like most length is gained in the nose.

Pic stolen from 24hcf

Also, your point with the stepped velocities doesn't seem to be at play, at least with Hornady's #'s. They step relatively in scale with each other I.E. there isn't much of a BC jump from 75 to 80 and a larger jump from 80 to 88, regardless of what mach is used.

 

[hereinaz]

The 180 ELDM is another one that baffles me. HUGE difference between hornady suggested BC and AB

Don’t think of BC as “one number” because it isn’t.

It is a number based upon a model shape that compares it to another model shape. Modeling is using science and math to predict, like weather forecasting is a model.

Weather is more unpredictable, but the principle is that it isn’t 2+2=4 math.

The BC changes depending on velocity, more significantly during supersonic and then less so after transonic and sub sonic.

AB and Hornady have the data, but Hornady chooses the number that sells the best to consumers who like to compare the box number and not look deeper. AB sells the data and puts it into their custom curve.

Look at this chart to show the difference between the “modeled” G1, G7, and reality of one bullet. This is why I choose AB custom curves.

 

[hereinaz]

The AB #'s would make sense if what you said was true but it appears that the changes are the opposite of what you're saying.

From 75-80 it looks like primary length is gained in bearing surface (and aligns with hornady listing the same min twist for both). From 80-88 it looks like most length is gained in the nose.

Pic stolen from 24hcf

Also, your point with the stepped velocities doesn't seem to be at play, at least with Hornady's #'s. They step relatively in scale with each other I.E. there isn't much of a BC jump from 75 to 80 and a larger jump from 80 to 88, regardless of what mach is used.

We are talking 5 grains of lead and copper, I wouldn’t trust eyeballing it. If someone measured it, that would be different.

We are talking the smallest of differences here on supersonic scales.

And, I am talking generally where the weight goes. Maybe I am wrong on where the shape vs weight makes the difference, I will have to read more if I can.

But, the principle is that there are diminishing returns in BC once the bullet reaches efficiency in aerodynamic shape.

 

[Formidilosus]

The difference in trajectory in the terminal range of bullets between using a G1 drag and a G7 is as close to meaningless as one can get- pole vaulting over mouse turds.
Likewise, the amount and precision of shooting that it requires to see the difference at 800 yards between a G1 Mach 2.25 and Mach 2.0 is far beyond what nearly anyone can or will do and see. For that matter, far beyond 800 yards.


AB tends to come up with lower BC values than Hornady does with Doppler. With Hornady ELD-M and X bullets, Hornady’s BC values have consistently proven to work to well beyond terminal ranges.


Using real G1/G7 BC values results in excellent shooting and precision.

 

[hereinaz]

This is where I have to dive back into my AB books to remember and figure it out…

It defies common sense because there are things going on under the hood to pick the numbers.

If I remember right, AB and Hornady have essentially the same BC numbers on the Doppler radar, but picking which BC to publish is a different choice between Hornady and AB.

Hornady chooses to publish numbers like girls choosing their best feature to show online.

Applied Ballistics is Moneyball, publishing numbers like baseball box scores.

 

[Formidilosus]

Hornady chooses to publish numbers like girls choosing their best feature to show online.

Applied Ballistics is Moneyball, publishing numbers like baseball box scores.

That’s generally true. With nearly all bullets AB’s BC numbers match real world very well…. Except Hornady’s. Dozens and dozens of shooters that I am around and everyone’s data that uses AB’s is off, yet does their data match’s Hornady’s very well.

 

[hereinaz]

The difference in trajectory in the terminal range of bullets between using a G1 drag and a G7 is as close to meaningless as one can get- pole vaulting over mouse turds.
Likewise, the amount and precision of shooting that it requires to see the difference at 800 yards between a G1 Mach 2.25 and Mach 2.0 is far beyond what nearly anyone can or will do and see. For that matter, far beyond 800 yards.


AB tends to come up with lower BC values than Hornady does with Doppler. With Hornady ELD-M and X bullets, Hornady’s BC values have consistently proven to work to well beyond terminal ranges.


Using real G1/G7 BC values results in excellent shooting and precision.

Love this point!

This is true, and AB essential says as much for hunting purposes. But, I may as well squeeze everything I can and use custom curves when my form sucks…

Go shoot is always the practical answer for hunting.

I am impractical nerding out, except if I can help people eliminate the confusion and stop the bad information that gets passed around.

Some people like to need out and others get wrapped around the axle worrying about it instead of shooting.

 

[hereinaz]

That’s generally true. With nearly all bullets AB’s BC numbers match real world very well…. Except Hornady’s. Dozens and dozens of shooters that I am around and everyone’s data that uses AB’s is off, yet does their data match’s Hornady’s very well.

Interesting.

I never thought Hornady numbers were “off” just they they pick a different BC than AB. And, like you said, in the real world G1, G 2, custom curve, not gonna matter for nearly all hunting.

Besides, prove your own data and true it as needed.

I shoot mostly Berger so I wouldn’t have that real world knowledge about Hornady. I will add that caveat.

I do know that Hornady bullet shooters like Hornady 4dof as well.

 

[Formidilosus]

Love this point!

This is true, and AB essential says as much for hunting purposes. But, I may as well squeeze everything I can and use custom curves when my form sucks…

Go shoot is always the practical answer for hunting.

I am impractical nerding out, except if I can help people eliminate the confusion and stop the bad information that gets passed around.

Some people like to need out and others get wrapped around the axle worrying about it instead of shooting.

There’s no doubt one can be a nerd with it all. The issue is for the vast majority of people they get bogged down in nonsense that has no value. They get inundated with “G1 versus G7 versus drag curve” and AJ, and everything else that has about .2% to do with hit rates, and completely ignore the 98.8% that actually matters.

 

[hereinaz]

Part of me likes to resolve the confusion that gets stirred up, so that new/uninformed shooters realize there is a lot of smoke, but no fire.

That’s where you bring reality to bear. And, when I go shooting I just go easy button and buy Berger Bullets, get good data for the AB solvers and go shoot.

Friends show up with all sorts of ammo and bullets, I plug it in and shoot. You are 100% right, because the vast majority don’t shoot well enough for me to trust their zero without a 20 round group, let alone long range shooting.

I think the bigger part of me is 100% nerd, lol. I bet a lot of shooters on this thread fall into it as well, including OP. I always watch for your comments to add reliable data points for my nerdy side.

 

[Godsdog]

There's a fair bit of discrepancy between AB's listed BCs and Hornady's for the ELDm line and it's not just a consistent % difference. For example, I always assumed the 75 ELDm had a better form factor than the 80 because the Hornady listed BC is very close. AB's #'s say the opposite.

	Hornady G7	AB G7
75​	0.235​	0.238​
80​	0.244​	0.258​
88​	0.274​	0.264​

Based on AB #s, the 80 ELDm looks really good for a balance of possible velocity and BC while Hornady's #'s make the 75 and 88 more attractive. When the 3 bullets are placed next to each other, the eye test indicates the BCs should align more with Hornady's BC progression - the 80 looks like just bearing surface added to a 75 at best, maybe even a shorter nose. The 88 looks like nose and boattail length added to an 80.

I'm curious on other's thoughts. Is this possibly just lot to lot variance on bullets that were tested?

There's a similar thing going on with the .257 134 grain and .264 140 grain - Hornady lists them at basically the same BC which to me suggests there would be very little benefit to the .25 creed vs 6.5 creed with these two bullets as the velocity benefit of the 134 should be small. However, AB #'s significantly favor the 134 so having a velocity, BC, and recoil advantage would give it the bigger edge.

I use AB custom curves for solutions rather than BC #s and realize this is mostly just noise in any of my real life applications but I found it interesting for discussion.

Maybe the difference is because they take their Chronograph Readings at the muzzle and the others take the reading down range, somewhere???

 

[hereinaz]

Maybe the difference is because they take their Chronograph Readings at the muzzle and the others take the reading down range, somewhere???

They are both using a sophisticated Doppler radar that tracks the bullet in space and time. They can pick a spot and tell you velocity and time of flight to that point, as well as location in the X and Y axis. I think they are able to track the X axis for lateral drift from wind deflection, spin drift, aerodynamic jump, and such.