- Thread starter dntworry
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You could get away with just adjusting velocity to match your drops if 800 is all you have to shoot. With that cartridge velocity is still the main determiner of trajectory at that range.
If you want to true at 800 for shooting long later, it's not gonna happen.
However, this will get you close. Take your initial BC and drop it 5%. That will be within a tenth or so out to 1500 yards. Your mid ranges will be a tenth or so high, but nothing horrible.
If you want to true at 800 for shooting long later, it's not gonna happen.
However, this will get you close. Take your initial BC and drop it 5%. That will be within a tenth or so out to 1500 yards. Your mid ranges will be a tenth or so high, but nothing horrible.
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How much are you off? 30fps = 0.1mil at 800 yards, that is a 1% change.
20 G7 BC points are needed to make the same change. Using round numbers, that is likely about a 5% or 6% BC change.
Which do YOU trust more?
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Don't use the truing feature as noted,
Use the real MV that you go from your Labrador, then at 800 true your BC Manually and align your 800-yard data to the BC.
If you have to tweak something inside 800 yards after, (adjusting the BC has very little effect inside 600) tune the MV but now the changes will be small and more meaningful.
Software that asks you to overmanipulate the MV as their only real method of truing is just wrong. So go outside the advertised way and true the BC then make minor adjustments to MV as needed.
Use the real MV that you go from your Labrador, then at 800 true your BC Manually and align your 800-yard data to the BC.
If you have to tweak something inside 800 yards after, (adjusting the BC has very little effect inside 600) tune the MV but now the changes will be small and more meaningful.
Software that asks you to overmanipulate the MV as their only real method of truing is just wrong. So go outside the advertised way and true the BC then make minor adjustments to MV as needed.
Lowlight,
I am using their CDM for my specific bullet the Berger 215 hybrid rather than a G1 or G7 drag should I switch back to be able to fudge the numbers?
Skookum,
I will have to do more testing this weekend but as an example I was on target at 805 using 17.5MOA and the AB app is suggesting 16.75MOA
I am using their CDM for my specific bullet the Berger 215 hybrid rather than a G1 or G7 drag should I switch back to be able to fudge the numbers?
Skookum,
I will have to do more testing this weekend but as an example I was on target at 805 using 17.5MOA and the AB app is suggesting 16.75MOA
Depending on how far the MV is off,
if the correction via your MV at 800 is more than 100fps, yes change back to a regular BC and adjust it, if the correction is say 25fps just change that number it's not too big
Knowing what the actual data is on target vs predicted would help answer this better
if the correction via your MV at 800 is more than 100fps, yes change back to a regular BC and adjust it, if the correction is say 25fps just change that number it's not too big
Knowing what the actual data is on target vs predicted would help answer this better
D
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I'm like a broken record saying this stuff, but so many people seem to be right at 1moa off. Which coincidently is about how much change optical effects often have.
Your solution could actually be spot on. When truing, try to do it either as early in the morning as possible or on an overcast day. Verify zero before moving out to distance. That will tell the tale.
Maybe you did this already, you didn't say.
If the BC you are using came from our library, and you are only shooting at 800 yards. Leave the BC alone. Sometimes any number of things can lead to the firing solution appearing to be off. But their is a simple rule of thumb to follow:
1) If the solution is slightly off in the Super Sonic range, like in your case, you want to adjust the MV. After you have made sure all other data is correct (Latitude, Firing Direction, Temp, Pressure etc.)
2) If the solution is off in the subsonic range, that is when you go into DSF. The reason for DSF over changing the BC, is because a BC is velocity dependent. By changing it, you can change the entire prediction model. But if you simply do a DSF, you will only change the "zone" so to speak that you are shooting in. But you are doing it to a specific speed of sound, which means that change will carry over properly with changes in atmospherics.
1) If the solution is slightly off in the Super Sonic range, like in your case, you want to adjust the MV. After you have made sure all other data is correct (Latitude, Firing Direction, Temp, Pressure etc.)
2) If the solution is off in the subsonic range, that is when you go into DSF. The reason for DSF over changing the BC, is because a BC is velocity dependent. By changing it, you can change the entire prediction model. But if you simply do a DSF, you will only change the "zone" so to speak that you are shooting in. But you are doing it to a specific speed of sound, which means that change will carry over properly with changes in atmospherics.
No, continue to use the CDM, and simply adjust MV if its in the Supersonic range or DSF if its in the Subsonic range.
Doc,
Why adjust the MV if I know it’s true? If my labradar is telling me what it is for every single shot why would I adjust it? If I’m shooting faster than the velocity you or anyone else used to calculate a BC why wouldn’t I adjust my BC and leave velocity alone?
Asking for f fiend.....
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the same time software with no real way of actually truing became the preferred method, that whacking the MV outside of the scope of realism was the answer, regardless of the Chronograph model or quality. I have to say when you see the software changing numbers by as much as 100fps+ that is not the chronograph in this case. Plus he is not shooting past 1000 yards.
We see truing the BC for the rifle and system, FIRST, a much better long-term and universal solution vs playing with MV at odd and long ranges. The OP does not have access to the necessary ranges to do it according to the software, hence his only real solution is to do it wrong or not at all. Going back in time and TRUING the BC for his rifle and system is a far better method, especially since you cannot adjust the CDM number.
The AB numbers are an AVERAGE based on THEIR rifle and system shot on that given day. (Doc can clarify but my understanding is most of these AB Averages are from 300 yards, not 800 like Hornady is doing) Look at the 308, the world used .496 at 2600-2650, yet they use .485, okay, just enough to be different, which is better? Truing the BC to a system specific average is just as easy and effective. And it does less damage to the curve when things change.
Coming from CO to sea level when truing via the Kestrel as advertised you always have to fix the MV at your destination. Might be small, 25fps, maybe 50fps, but when we started ignoring the truing feature and doing it manually via BC first that all went away. The solution I trued via this method worked in Tennessee shooting and carried over and worked in NM shooting to 2000 yards. All 3 locations were spot on.
I would much rather have a trued BC than an over-tweaked MV that is 100fps outside what was read. If the software, in this case, was perfect we could and WOULD all throw our chronographs away save the money and just let the software pick a new number and in the software's case, a necessary number for us and we would just drive on letting it figure it out vs buying a chronograph.
Funny I just got back from recording a podcast with Brian Whalen regarding the 224V and he unprompted mentioned his trued BC for the 88gr Hornady and I mentioned I was using the Mach 2.0 value for my AB Kestrel. I had 3 choices in BC from Hornady, Mach 2.5, Mach 2.0 and Mach 1.5 that is their advertised solution. Brian is using .269 G7, the Average is .274... Using a 26" barrel, handloads, he reduced it to .269 Tiny I know but valuable information nonetheless. G1 value on the specs is .545, however, I am using .534 for my AB solver, another example of the same tweak vs having to mess with a fake MV.
I honestly think it screws people up who may only have access to 600, 800, 1000 yards or less when the software says true this at 1400+. I think they just move on and ignore it because they figure they cannot do it right because of lack of access. Well, they can, true the BC First and the MV adjustment is noticeably smaller. Let them adjust the CDM in the kestrel first and MV later and bang problem solved.
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I'm pretty sure we are in agreement on things. I prefer to use MV at the closer ranges 800 and closer, because chronos aren't perfect and neither are the operators. And...subtle tweaks in velocity have much more effect at closer ranges than BC does. But as you said, within a very narrow range of 1% or less.
Beyond that, if the closer ranges line up, I'm all about some BC change.
Thing is though, once you get out to distance, if you aren't accounting for or controlling for optical effects you just aren't gonna get good data. Light will fuck up a data set in a heartbeat, and it is the least talked about and least understood aspect.
I had a light condition last week that was worth almost 0.5 mils. It was completely canceling a 3mph wind at 902 yards. That kind of difference in the vertical, if you didn't realize it, would do some real damage to any attempt at truing.
Beyond that, if the closer ranges line up, I'm all about some BC change.
Thing is though, once you get out to distance, if you aren't accounting for or controlling for optical effects you just aren't gonna get good data. Light will fuck up a data set in a heartbeat, and it is the least talked about and least understood aspect.
I had a light condition last week that was worth almost 0.5 mils. It was completely canceling a 3mph wind at 902 yards. That kind of difference in the vertical, if you didn't realize it, would do some real damage to any attempt at truing.
For sure, we are in the weeds with this, agreed.
but when the average end user does not have access to the ranges necessary to properly use the feature, a replacement method is necessary.
but when the average end user does not have access to the ranges necessary to properly use the feature, a replacement method is necessary.
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Drop Scale Factor
its a multiplier the software apples in the transonic and subsonic region to more accurately predict hits.
Went out this weekend, great day little to no wind. Had issues with the .300WM but using my 6.5 had the same data mismatch.
Steps performed:
Re-zero
Re-chrono
Check scope level with a tall target and a 6ft level
Tall target tests show my NF elevation tracking at 100% up to 30 MOA (did not test windage as I typically hold for wind)
Entered data into Strelok Pro and AB - both gave different results varying 0.5-1.25 MOA depending on range. Strelok was right on within 1 click of perfect out to 800 and AB was always off.
Using a 143gr ELDX with the AB DSF for this bullet - I was able to tweak the MV to get it to line up better after getting back home and playing with the numbers but never got it to match perfectly with what I was seeing. I feel like I have to be doing something wrong with data entry in AB to be that far off.
Ideas?
Steps performed:
Re-zero
Re-chrono
Check scope level with a tall target and a 6ft level
Tall target tests show my NF elevation tracking at 100% up to 30 MOA (did not test windage as I typically hold for wind)
Entered data into Strelok Pro and AB - both gave different results varying 0.5-1.25 MOA depending on range. Strelok was right on within 1 click of perfect out to 800 and AB was always off.
Using a 143gr ELDX with the AB DSF for this bullet - I was able to tweak the MV to get it to line up better after getting back home and playing with the numbers but never got it to match perfectly with what I was seeing. I feel like I have to be doing something wrong with data entry in AB to be that far off.
Ideas?
Post screenshots of your data pages or include all the information you are using.
We need to SEE what you are doing because you are only giving us a partial story.
We need everything, Actual Dope, Ranges, and then Inputs being used. AB could be 100% and you just have one thing screwed up.
We need to SEE what you are doing because you are only giving us a partial story.
We need everything, Actual Dope, Ranges, and then Inputs being used. AB could be 100% and you just have one thing screwed up.
What is your actual MV not the corrected MV
Besides what Strelok Predicted, what is the actual elevation at the target, in other words did you write it down.
2400fps is super slow I hope that is what the software did, being that slow your BC is definitely not gonna work. So the Custom Curve will be off, as I am sure the Custom Curve is based on a standard MV and not something 200fps + too slow
Besides what Strelok Predicted, what is the actual elevation at the target, in other words did you write it down.
2400fps is super slow I hope that is what the software did, being that slow your BC is definitely not gonna work. So the Custom Curve will be off, as I am sure the Custom Curve is based on a standard MV and not something 200fps + too slow
I do not have the specific elevation at the target but the range weather station reports 1124 ft, the station pressure I wrote down was from my Kestrel 2500 with reference alt set to 0.
If it’s not a real load don’t worry about. Do your load development then true it up
The Averaged G7 BC should provide accurate results in supersonic range. If something in the the rifle has caused a slight variation from the prediction, then tweaking the MV often works for users. The Kestrel used to have SSF, and after much testing and user feedback we found that simply adjusting the MV had the same effect. Simplfying things by removing it, and just using MV Cal. Variation in BC is generally not large before you hit transonic. This is speaking generally, because their are some exceptions. Mostly poor bullet design.
BCs are misunderstood. Adjusting them, can often and does often lead to problems that creep up later on. Using the lab data, and calibration tools has been the most successful method for refining solutions. If adjusting the BC worked better, I would certainly suggest that as it is always my goal to suggest best and most successful practices.
For me,
I look at what Hornady has done, having spent several days in NE with them, and getting a class on their methodology, I want to tune the BC. Here is part of my justification for it, the Curves as outline in the Hornady Data:
Twist Rate Curve Spread
Rifling Effects
Muzzle Brakes
Powder Charge
Other factors,
They have moved to the Axial Form Factor which changes the way we address it, but at the same time they talk BC over MV
So they go into truing of the BC
Using just the MV is a working solution but limited in my opinion as these variations will change thus causing issues down the road. MV is not something that stays exactly the same.
A lot of the data used to justify stuff being good enough for what we are doing assumed we all shot relatively short ranges. If you go back and read the original data a lot of these early manuals and ballistic data was for 700 yards and in, most of them are for 400 yards and closer. That is why we SEE the changes now. These changes require we address the issue in a different way.
I think for AB specific issues, the MV stuff works, within reason, but we find to get a better solution, work the BC then make minor tweaks to the MV.
Even David Tubb in my Podcast with him speaks in-depth about working and managing the BC. He talks about a wandering BC valid even if the load has an SD of 0 (zero), that he will see minor fluctuations in the BC value.
We have two choices for sure, MV or BC, I think the more we stretch our legs, the more we'll fine-tune our approaches.
I look at what Hornady has done, having spent several days in NE with them, and getting a class on their methodology, I want to tune the BC. Here is part of my justification for it, the Curves as outline in the Hornady Data:
Twist Rate Curve Spread
Rifling Effects
Muzzle Brakes
Powder Charge
Other factors,
They have moved to the Axial Form Factor which changes the way we address it, but at the same time they talk BC over MV
So they go into truing of the BC
Using just the MV is a working solution but limited in my opinion as these variations will change thus causing issues down the road. MV is not something that stays exactly the same.
A lot of the data used to justify stuff being good enough for what we are doing assumed we all shot relatively short ranges. If you go back and read the original data a lot of these early manuals and ballistic data was for 700 yards and in, most of them are for 400 yards and closer. That is why we SEE the changes now. These changes require we address the issue in a different way.
I think for AB specific issues, the MV stuff works, within reason, but we find to get a better solution, work the BC then make minor tweaks to the MV.
Even David Tubb in my Podcast with him speaks in-depth about working and managing the BC. He talks about a wandering BC valid even if the load has an SD of 0 (zero), that he will see minor fluctuations in the BC value.
We have two choices for sure, MV or BC, I think the more we stretch our legs, the more we'll fine-tune our approaches.
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So, is Hornady advocating altering the BC, or the Cd (axial form factor as they call it )?
For their software, Axial Form Factor is the preferred solution as it addresses the entire curve and not just points within.
For other software, BC first, MV second as noted
For other software, BC first, MV second as noted
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