.338 270gr ELDx verified bc results

300 Driver

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I'm looking for real world data on the G7 BC for the 270gr eldx

I recently verified drops at 600, 800, and 1000yds and had to drop the BC from factory claimed .381G7 to a .345G7 to make my ballistic app match real world. I could also make the app match by dropping 40fps from my 5-shot chrony avg and keeping the advertised bc.

Bullet Drop plus app
1000' MSL
86% humidity
78F
30.12

33SM @2748fps off a magneto speed.

I'd like to hear what everyone else uses for this bullet's G7. Thanks in advance!
 
Last edited:
BC will vary from rifle system to rifle system. Also it will vary from day to day with different atmospheric conditions. How the bullet is engraved by individual barrels will change the bc.
Agreed! Allow me to reword the question.

I'm not used to a 10% change from advertised BC across the other rifle systems I load for also using AMax and ELDm(6mm and 7mm). That is why I am looking for data from users of this specific projectile. Are other users of the 270gr eldx seeing similar BC numbers?
 
I will bet if that bullet was shot outside of the 'window' pertaining to velocity, read higher, then the BC will increase.
BC changes with velocity and is not a constant.
When we developed our solid CNC turned target VLD bullet, the computer said xx BC, it is 323g .338" cal and has a real world BC G7 .397 at 3150fps. It is actually shot at 3070fps average, losing about 2% BC.
If your BC is changing from advertised, then advertised MUST BE inflated. I know this was true with Nosler ABLR when first introduced, we couldn't get close with the heavies in 338 cal…

Cheers.
 
I will bet if that bullet was shot outside of the 'window' pertaining to velocity, read higher, then the BC will increase.
BC changes with velocity and is not a constant.
When we developed our solid CNC turned target VLD bullet, the computer said xx BC, it is 323g .338" cal and has a real world BC G7 .397 at 3150fps. It is actually shot at 3070fps average, losing about 2% BC.
If your BC is changing from advertised, then advertised MUST BE inflated. I know this was true with Nosler ABLR when first introduced, we couldn't get close with the heavies in 338 cal…

Cheers.
The reason I am asking for actual users of this bullet are that Litz found the eld advertised BCs to be very close to his numbers for 6.5 and .308 bullets according to a few searches around the web. But I have not seen Litz numbers for the .338 cal 270gr ELDx. Therefore, I am looking for actual data from users of this projectile.

I understand how BCs are calculated and the scenario you mention is why Sierra lists 3 BCs for velocity ranges. I have not seen such info from Hornady and a 10% BC loss (from .381 to .345) is well outside what I can see as the norm for most vld profile bullets.

I suspect that the advertised BC is not exact, but I'd like to compare to other real world data. I also think my old magnetospeed may not be as accurate as it once was…

Is there anyone out there who has confirmed BC data on the .338 cal 270 ELDx??
 
I agree, just looking to confirm if I have a wildly inaccurate advertised BC or a bad chrony before dropping $600 on a Xero. That's why the request for real world data. For employing the weapon system, I trust DOPE over all sources for that specific weapon.
 
The reason I am asking for actual users of this bullet are that Litz found the eld advertised BCs to be very close to his numbers for 6.5 and .308 bullets according to a few searches around the web. But I have not seen Litz numbers for the .338 cal 270gr ELDx. Therefore, I am looking for actual data from users of this projectile.

I understand how BCs are calculated and the scenario you mention is why Sierra lists 3 BCs for velocity ranges. I have not seen such info from Hornady and a 10% BC loss (from .381 to .345) is well outside what I can see as the norm for most vld profile bullets.

I suspect that the advertised BC is not exact, but I'd like to compare to other real world data. I also think my old magnetospeed may not be as accurate as it once was…

Is there anyone out there who has confirmed BC data on the .338 cal 270 ELDx??
it's not that different because Hornady and Litz both are using Doppler to measure the bullets.

They are what they are.

As to why you're not getting published BCs, is because they run those samples of a test barrel.
They are never the same rifle to rifle, which others above have explained.

This has more to do with YOUR barrel, YOUR velocity, and YOUR atmospherics. This can be summarized as MACH, which Hornady publishes.


Linked here:https://www.hornady.com/support/ballistic-coefficient


And is as follows:

338 Cal 270 gr. ELD-X
Mach 2.5
0.757 G1
0.381 G7

Mach 2.0
0.745 G1
0.374 G7

Mach 1.75
0.739 G1
0.372 G7

Poor truing habits is another thing I've seen throw people off. Don't go adjusting BC to change your dope, within supersonic. Adjust BC around or after Transonic.

Or better yet, if you use AB, opt for a custom curve, they work better.
 
it's not that different because Hornady and Litz both are using Doppler to measure the bullets.

They are what they are.

As to why you're not getting published BCs, is because they run those samples of a test barrel.
They are never the same rifle to rifle, which others above have explained.

This has more to do with YOUR barrel, YOUR velocity, and YOUR atmospherics. This can be summarized as MACH, which Hornady publishes.


Linked here:https://www.hornady.com/support/ballistic-coefficient


And is as follows:

338 Cal 270 gr. ELD-X
Mach 2.5
0.757 G1
0.381 G7

Mach 2.0
0.745 G1
0.374 G7

Mach 1.75
0.739 G1
0.372 G7

Poor truing habits is another thing I've seen throw people off. Don't go adjusting BC to change your dope, within supersonic. Adjust BC around or after Transonic.

Or better yet, if you use AB, opt for a custom curve, they work better.
First, thank you for the link. I was not aware of that data. It seems to confirm that my adjusted BC of .345 is significantly low.

As to what you and MM and RockyMt have stated, I do not disagree with the information you all have stated. But it did not answer my question. It did answer how variables affect BC calculations and why that happens, but my questions is what BC are others using. Have you actually used the .338cal 270gr ELDx? If so, What data did you input for BC into your ballistic app?

I believe I have an equipment problem I am trying to troubleshoot. Maybe my Magnetospeed is no longer within specs, maybe my ballistic app sucks, or maybe others see SIMILAR, NOT EXACT data to my experience and I'm just fine. I'll look into the AB app and the custom curve, that sounds pretty cool, always happy to find a more accurate solution.

As to trueing habits, this is my process after zeroing with a chosen load. Maybe this is contributing?
1) input advertised G7 BC and 5-shot chrony avg velocity plus environmental from kestrel and gun details into app
2) shoot at 600, 800, and 1000 and record DOPE ( repeat this step at least 3 times over different days) in field conditions
3) adjust BC or speed, but not both, to get app to match real world data.
I commonly harvest game in the 800 and less range, hence the chosen ranges.

I read more than I type on his forum and I think the educational information can be awesome, but I think the previous responses jumped to education, when all I asked for was data. I have reviewed my DOPE again and realized my wind inputs were very close(within my shooting capabilities), it was only the elevation that needed adjustment. I am leaning towards chrony error.
 
This is very much like asking for an answer to what BC has been attained by pointing bullets…it is always higher, but often it's not enough to calculate fully.
The answer to this is often difficult to quantify because one ballistic app says one thing and another one is different depending WHICH numbers the program uses to calculate the BC.
What @dfanonymous says is spot on about what you change to get the true BC.

Cheers.
 
Do you have another 30 cal? You could run it in another rifle and see how your results compare. I don't think you are having an equipment issue. I think it is this particular rifle and scope.

I have not shot this bullet so I apologize for not giving you the personal data you are looking for. I can tell you that I have seen much bigger variations in bc from rifle to rifle with the same bullet than what you are seeing. I have been beat up on this sight for it many times. The fact is it happens to any bullet and bc is not a constant.

My guess is your mag speed is still good but I highly recommend the Garmin. It is so easy!
 
I'm looking for real world data on the G7 BC for the 270gr eldx

I recently verified drops at 600, 800, and 1000yds and had to drop the BC from factory claimed .381G7 to a .345G7 to make my ballistic app match real world. I could also make the app match by dropping 40fps from my 5-shot chrony avg and keeping the advertised bc.

Bullet Drop plus app
1000' MSL
86% humidity
78F
30.12

33SM @2748fps off a magneto speed.

I'd like to hear what everyone else uses for this bullet's G7. Thanks in advance!
Download my app and you can make your own BC for your gun
Eagle Ballistics
 
I'm looking for real world data on the G7 BC for the 270gr eldx

I recently verified drops at 600, 800, and 1000yds and had to drop the BC from factory claimed .381G7 to a .345G7 to make my ballistic app match real world. I could also make the app match by dropping 40fps from my 5-shot chrony avg and keeping the advertised bc.

Bullet Drop plus app
1000' MSL
86% humidity
78F
30.12

33SM @2748fps off a magneto speed.

I'd like to hear what everyone else uses for this bullet's G7. Thanks in advance!
 
Have you tried Hornady's 4DOF ballistic app? Since you are trouble shooting, it never hurts to get a second opinion. 4DOF has been quite good for me with Hornady products.

Also, how statistically significant was your verification testing? Could the error be in your testing?
  1. Was the group size sufficient to rule out normal distribution bias (e.g. 8-12 shots per distance)?
  2. Could there have been an unaccounted for head wind, or left to right crosswind that lowered your impact point a smidge?
  3. Did you have your atmospheric conditions spot on (e.g. measured with a weather meter and barometer on site at the time?)
  4. Velocity from a 5 shot group? Doubt that would have you off by 40 fps, but I could easily see it being 20 fps.
Despite what some claim, B.C. should not vary by -10% from quoted. Manufacturers of course want you to believe that's "normal variation from rifle to rifle", as it allows them to get away with inflated B.C. values to boost sales, but if that was the case, where are the other half of the forum posts where people are complaining about impacting way high because the B.C. is actually 10% higher than the manufacturer claims...
 

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