Are manufacturers Bullet BC total BS?

[robby denning]

My Berger bullets ran through Vortex’s LRBC program lined up perfectly at 600 and 700 yards in drop. So I can only assume the BC that I put in the formula was correct.


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[ajwcotton]

To try to diagnose ballistic app errors we have to know all your inputs and the environmentals from when you were shooting.
Also what app and what chronograph were you using?
If you are an entire mil off at 1k you have a bad input somewhere. I can't think of anyone who has their bc's that far off. Also hornady has their own doppler radar as well, and their 4dof app is derived from that data so it would be very very close to real world dope if your inputs are correct.

 

[TheCougar]

To answer a bunch of questions:
- I don't remember what type of chrono or how far. I just remember it was attached to the muzzle.
- I used the Hornady and another app and got similar numbers.
- I have not done the ladder test, so Justin's recommendation to make sure that a "mil is a mil" is a really good thought that hadn't occurred to me.
- I'm on the road for a while, so I can't go home and check all the numbers.

Suffice it to say that I probably screwed something up somewhere, either in the calculations, the raw data I used for the calculations, or my scope is not perfect. I appreciate all the input and I have some good things to start running down.

 

[LaHunter]

To answer a bunch of questions:
- I don't remember what type of chrono or how far. I just remember it was attached to the muzzle.
- I used the Hornady and another app and got similar numbers.
- I have not done the ladder test, so Justin's recommendation to make sure that a "mil is a mil" is a really good thought that hadn't occurred to me.
- I'm on the road for a while, so I can't go home and check all the numbers.

Suffice it to say that I probably screwed something up somewhere, either in the calculations, the raw data I used for the calculations, or my scope is not perfect. I appreciate all the input and I have some good things to start running down.

chrono attached to muzzle sounds like a Magneto chrono. These provide accurate velocity data, but they do effect POI significantly, according to most reviews. This is the downside of the Magneto. you need to remove the chrono before verifying your dope/shooting for groups

 

[TheCougar]

chrono attached to muzzle sounds like a Magneto chrono. These provide accurate velocity data, but they do effect POI significantly, according to most reviews. This is the downside of the Magneto. you need to remove the chrono before verifying your dope/shooting for groups

I definitely saw that! None of the chrono shots were used since they were so far off. Just used the velocities we got.

 

[wind gypsy]

BC varies by rifle. Rifles deform and stabilize bullets differently. It is possible your effective BC is less than hornady advertises but not enough to be a mil off @ 1000 @ 2665 FPS (assuming creedmoor ammo) IMO.

There could be multiple issues compounding - environmentals (people mess up things sometimes when multiple enviro factors need to be entered), a down draft, a scope that doesn't adjust properly, etc. It wouldn't take much if the bullet is actually working out to 0.57 G1 and other factors are compounding.

 

[Pacific_Fork]

chrono attached to muzzle sounds like a Magneto chrono. These provide accurate velocity data, but they do effect POI significantly, according to most reviews. This is the downside of the Magneto. you need to remove the chrono before verifying your dope/shooting for groups

Thanks for this advice as I had no idea. I always leave the Magneto on while testing long range ballistics, yikes. Might have found at least part of my problem...

 

[WCB]

This may sound stupid...did you put the correct BC in? I have seen guys put in the G1 instead of the G7 when the app calls for G7. Also, is the height of your optic correct?

 

[BRTreedogs]

I had a similar problem with my man bun the other day.
I was hammering at 700 but at 900 wasn't close.

Well the applied ballistic app had the bc number backwards.
So when I selected the 147 M the BC was completely off. The had some number reverse.
Like .513 instead of .315 G1

 

[msstate56]

Just go back through you ballistic app line by line. Just one variable being off will ruin your data. Especially check you sight over bore height. If that is off it will really start to show at distance. Whenever you start seeing large abnormalities, it’s usually because an input is wrong in the app.

 

[msstate56]

BTW- try using the banded BC numbers Hornady puts out. Since I’ve started using the banded numbers- I just verify my MV at 500-600 yards and my data has been spot on out past 1000.

 

[carter33]

I recently shot the 143 eldx out of a 6.5PRC stepping from 100 out to 1000 using 2.94(applied ballistics value for the bullet) as my BC with a MV of 2944fps. All of the calculations from applied ballistics were spot on and verified, this was at a shooting course so I had some profesional help/verification. The above post is probably leading you in the right direction using a BC just slightly under the BC I used due to MV being lower.

I have heard that it is best to adjust MV out to 600 then BC out beyond that when tuning a ballistics solver unless you are extremely confident in the chronograph and have a large sample.

 

[Outdoorsman12b]

I went out with a shooting instructor last month and shot 200 rounds of 6.5 ELDX over the course of the day, from 100-1000 yards. We chronographed the bullets and the actual dope was waaaay off the ballistic app prediction. At 1000 yards I had to dial an extra 10 clicks to compensate for drop (mrad). The velocity was 35fps slower on average than the Hornady numbers, but that didn’t account for the large difference. I had the environmentals correct and I can’t figure out if there is something else wrong or if the BC was just that optimistic. It was pretty consistent too - the deviation increased as the range increased, so it sure looked like the bullet was slowing down much faster than anticipated.

That's a lot faster than I get out of my tikka. I average 2575fps. I have not found that variance you speak of at 900 yards (farthest at my range). Just wondering what the mirage was doing and how hot your barrel was? I have found low POI when my barrel heats up and if mirage is bad.

 

[BRTreedogs]

So apparently yes they can be bs.
I contacted applied ballistics about what I found to be an incorrect bc in the kilo app.
For the 6.5 147 eldm is listed a G7 of .315 instead of .351
He said in because the .351 number was at mach 2.25 it did not work well past 600 yards.
Mach 1.75 is a better speed for real world and what they found was correct. And Hornady had also listed .321 on there website.
I did some more digging and here is a link to some I fo Hornady put out. I'm a little disappointed I had to dig so hard to find it as I had already looked at the site a couple times.

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

 

[wind gypsy]

So apparently yes they can be bs.
I contacted applied ballistics about what I found to be an incorrect bc in the kilo app.
For the 6.5 147 eldm is listed a G7 of .315 instead of .351
He said in because the .351 number was at mach 2.25 it did not work well past 600 yards.
Mach 1.75 is a better speed for real world and what they found was correct. And Hornady had also listed .321 on there website.
I did some more digging and here is a link to some I fo Hornady put out. I'm a little disappointed I had to dig so hard to find it as I had already looked at the site a couple times.

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

View attachment 188587

Hornady has been pretty open about this and there are a fair amount of links that redirect to the ELD/Atip BC page. They even show varying BC based on twist rate for some bullets.

 

[TheCougar]

So apparently yes they can be bs.
I contacted applied ballistics about what I found to be an incorrect bc in the kilo app.
For the 6.5 147 eldm is listed a G7 of .315 instead of .351
He said in because the .351 number was at mach 2.25 it did not work well past 600 yards.
Mach 1.75 is a better speed for real world and what they found was correct. And Hornady had also listed .321 on there website.
I did some more digging and here is a link to some I fo Hornady put out. I'm a little disappointed I had to dig so hard to find it as I had already looked at the site a couple times.

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

View attachment 188587

I’m not too proud to admit I have no idea what all you guys are talking about with Mach, g1, and g7. I just plugged in whatever BC was on the Hornady website, chrono-ed 10 rounds from a few boxes, did an average speed dispersion and plugged in the numbers. Obviously I have a lot to learn!

 

[TheCougar]

That's a lot faster than I get out of my tikka. I average 2575fps. I have not found that variance you speak of at 900 yards (farthest at my range). Just wondering what the mirage was doing and how hot your barrel was? I have found low POI when my barrel heats up and if mirage is bad.

It was cold, no mirage from the barrel. I was shooting a Hells Canyon Speed. I don’t think the barrel got too hot. It took 8 hours to shoot 200 rounds, mainly in small bursts of 3-10 rounds.

 

[270quest]

The BC listed on the 150 .284 scenar is .526 if I remember right...My test at 3000' launching them in a 9.5 twist tikka at 3100 FPS validated them to be close .460-.465. My load data per the shooting app was off 1 full MOA at 500 yards.

 

[BRTreedogs]

I’m not too proud to admit I have no idea what all you guys are talking about with Mach, g1, and g7. I just plugged in whatever BC was on the Hornady website, chrono-ed 10 rounds from a few boxes, did an average speed dispersion and plugged in the numbers. Obviously I have a lot to learn!

Basically long story short hornady cherry picked the bc they are putting on the box.
Applied ballistics posts a more real word bc.

Is the bc you used the same as the one I screen shot for you above?
If not try that. It is hornadys revised.

 

[wind gypsy]

Basically long story short hornady cherry picked the bc they are putting on the box.
Applied ballistics posts a more real word bc.

Is the bc you used the same as the one I screen shot for you above?
If not try that. It is hornadys revised.

Hornady publishes g1 and g7 BC based upon 3 different machs as measured by doppler radar. I'd give em a pass.

Applied ballistics revises BCs as well.