Shoot2Hunt University

[Coleredding00]

@Formidilosus thanks for all the information you’ve shared on here and the podcasts.

This piggybacks off @TimberHunter’s question. I have heard other folks (outside of the TMK discussion) adjust their BC when trueing.
Could you please elaborate on why you shouldn’t “touch real BC numbers on bullets?”

Apologies if you’ve explained this somewhere else.

Thanks again.

I am curious on the reason for this as well. I have always had to true BCs on bullets to line up dope. Changing the velocity that i have actually measured and observed in the present environmental conditions and just believing the bullet mfg to be honest and correct seems strange... bullets like the 180 ELDM are notorious for dishonest BCs, and different bullets from different twists at different mach values will have different BCs.

 

[3gunyotehtr]

I have always adjusted bc as well. I'm not changing velocity if I know that it is correct, but bc does vary small amounts between rifles, and most of the time it doesn't take much change to make it line up with actual data. Even doppler testing on the same bullet by different facilities will often give different numbers.

 

[longrangelead]

Another convert...

Seeing and doing is believing.

 

[Formidilosus]

I have always adjusted bc as well. I'm not changing velocity if I know that it is correct, but bc does vary small amounts between rifles, and most of the time it doesn't take much change to make it line up with actual data. Even doppler testing on the same bullet by different facilities will often give different numbers.

How much does BC change between rifles when measured? And are you chronoing every shot at range while you are trueing BC at the same time? How do you know that your scope is adjusting at 100%- are you checking every scope through the full range of travel?

 

[Coleredding00]

How much does BC change between rifles when measured? And are you chronoing every shot at range while you are trueing BC at the same time? How do you know that your scope is adjusting at 100%- are you checking every scope through the full range of travel?

Yes, i only adjust BC while actively chronographing. Usually it only takes +\- .003 or so to correct any issues.

Scope tracking error is something that i have considered in this process. Never measured it to check if it correlates with the adjustment to BC. It’s entirely possible that it does, and i am using bc to correct for it, as AB doesn’t have a scope tracking correction. The end result seems to be the same either way, as long as dope lines up. I guess i just don’t see why one would adjust a variable that can be measured in real time and known to be true? Genuine questions, this is the only method I have ever known or been taught.

 

[Nine Banger]

Changing the velocity that i have actually measured and observed in the present environmental conditions and just believing the bullet mfg to be honest and correct seems strange...

I'm not changing velocity if I know that it is correct

What chrono do y'all use?

I had to correct muzzle velocity in Shooter App when I had a magnetospeed while using the BC from the bullet manufacturer.

Since I got the Garmin the calculations have been correct while using the BC from the bullet manufacturer.

 

[Coleredding00]

What chrono do y'all use?

I had to correct muzzle velocity in Shooter App when I had a magnetospeed while using the BC from the bullet manufacturer.

Since I got the Garmin the calculations have been correct while using the BC from the bullet manufacturer.

Personally i use a LabRadar. I’ve ran it next to garmins and it’s been consistent.

 

[Speaks]

What chrono do y'all use?

I had to correct muzzle velocity in Shooter App when I had a magnetospeed while using the BC from the bullet manufacturer.

Since I got the Garmin the calculations have been correct while using the BC from the bullet manufacturer.

I like the garmin, not sure that its better but it sure is simple and very compact to throw in a range bag.

 

[Nine Banger]

Personally i use a LabRadar. I’ve ran it next to garmins and it’s been consistent.

A guy at my club has one he is always screwing around with it and balancing plywood and cardboard scraps between it and the shooter to get it to produce a reading.

 

[Nine Banger]

I like the garmin, not sure that it's better but it sure is simple and very compact to throw in a range bag.

It's better.

The Magnetospeed produced data that wasn't consistent with what the rifle was actually doing.

The Garmin produces data that provides hits.

With most of the stuff I'm shooting 25fps will move my cone .1 mil. That's close to 1% error. The Magnetospeed was usually off 3-4%. Close enough at the time now it's obsolete.

 

[Coleredding00]

A guy at my club has one he is always screwing around with it and balancing plywood and cardboard scraps between it and the shooter to get it to produce a reading.

Seems that they can be hit and miss. If i use the trigger when suppressed and aim it properly i dont miss many shots. But they are definitely less forgiving than a garmin.

 

[TimberHunter]

Yes, i only adjust BC while actively chronographing. Usually it only takes +\- .003 or so to correct any issues.

Scope tracking error is something that i have considered in this process. Never measured it to check if it correlates with the adjustment to BC. It’s entirely possible that it does, and i am using bc to correct for it, as AB doesn’t have a scope tracking correction. The end result seems to be the same either way, as long as dope lines up. I guess i just don’t see why one would adjust a variable that can be measured in real time and known to be true? Genuine questions, this is the only method I have ever known or been taught.

You can shoot well enough to notice a change in .003 BC?


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[Coleredding00]

You can shoot well enough to notice a change in .003 BC?


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When trueing with 10 round groups at 1000-1200 yards, you can see it. That is how i true. Shoot a 10 round group on a large plate at 1000 yards and change BC in the calculator to adjust the solution to what was observed.

The same could be said for “can you shoot well enough to notice a change in 10 fps?”

There’s a reason people line up to shoot their rifles over the AB Doppler at matches to get a Custom drag profile from their rifle with their lot of bullets. BC fluctuates. Rifling engraving profiles from different barrel manufacturers, lot numbers of bullets. It can all have a measurable effect on BC. This is a proven concept that Brian Litz has scientifically proven. Is it the largest factor in the equation for an hunting rifle in hunting scenarios? Absolutely not. But it can’t be dismissed that the BC number printed on a box of bullets can’t be treated as the gospel when it has been proven that they can vary.

 

[Nine Banger]

You can shoot well enough to notice a change in .003 BC?


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How much do you have to adjust BC to shift your calculated drops .1 mil from 0-600 yards?

I was being passive aggressive about holding MV data collected on consumer electronics to be true versus published BC by a maker.

 

[wind gypsy]

Yes, i only adjust BC while actively chronographing. Usually it only takes +\- .003 or so to correct any issues.

Scope tracking error is something that i have considered in this process. Never measured it to check if it correlates with the adjustment to BC. It’s entirely possible that it does, and i am using bc to correct for it, as AB doesn’t have a scope tracking correction. The end result seems to be the same either way, as long as dope lines up. I guess i just don’t see why one would adjust a variable that can be measured in real time and known to be true? Genuine questions, this is the only method I have ever known or been taught.

Interesting on the bolded. There are tracking correction factor on kestrel and within my AB rangefinder ballistic solutions.

I test all of my scopes for tracking with a static scope mount on the calibrated target linked below at a tape verified 100 yards. If clicks are off slightly by a consistent value, that can be entered into my kestrel or RF solution.

Store - Box to Bench Precision

Snipers Hide 100 Yard Scope Tracking Target - MIL - MOA - For Milliradian and Minute of Angle Scopes - True Minute of Angle - Precision Shooting -

www.boxtobenchprecision.com

 

[Coleredding00]

Interesting on the bolded. There are tracking correction factor on kestrel and within my AB rangefinder ballistic solutions.

I test all of my scopes for tracking with a static scope mount on the calibrated target linked below at a tape verified 100 yards. If clicks are off slightly by a consistent value, that can be entered into my kestrel or RF solution.

Store - Box to Bench Precision

Snipers Hide 100 Yard Scope Tracking Target - MIL - MOA - For Milliradian and Minute of Angle Scopes - True Minute of Angle - Precision Shooting -

www.boxtobenchprecision.com

I guess I should’ve been more clear, the version of applied ballistics that my vortex fury binoculars use does not have a scope tracking correction to my knowledge. I don’t own an kestrel and don’t use a AB quantum.

 

[wind gypsy]

I guess I should’ve been more clear, the version of applied ballistics that my vortex fury binoculars use does not have a scope tracking correction to my knowledge. I don’t own a kestrel and don’t use a AB quantum.

Gotcha.

In the old sig app for my Kilo 2400 ABS it looks like i'd need to be paired to the RF and "calibrate" to enter such a thing.

In quantum:


In BDX:

 

[LBWV]

Because “real” BC numbers- Doppler, Oehler 88, etc.; are producing real numbers for BC. Rifle to rifle variation does not vary enough to see with live shooting without huge amount of rounds in very controlled environments, at very long range.

It takes a large difference in BC to cause noticeable shifts in the terminal range of bullets, much larger than is seen in rifle to rifle variation. So when people start messing with BC, they are just getting themselves in a tissy and muddying the waters.

@Formidilosus thanks for taking the time to explain that. Really appreciate it.

 

[3gunyotehtr]

What chrono do y'all use?

I had to correct muzzle velocity in Shooter App when I had a magnetospeed while using the BC from the bullet manufacturer.

Since I got the Garmin the calculations have been correct while using the BC from the bullet manufacturer.

Garmin

 

[Formidilosus]

When trueing with 10 round groups at 1000-1200 yards, you can see it. That is how i true. Shoot a 10 round group on a large plate at 1000 yards and change BC in the calculator to adjust the solution to what was observed.

No, you cannot see .003 change in BC. For the people reading, this is the nonsense that is caused by people trying to be engineer dorks instead of shooting and experimenting themselves. People believing that they can control things that are way outside of their ability.

1,200 yards 7PRC 180gr ELD-M. .003 change in BC.






6cm 112 MatchBurners, .003 change in BC-

The same could be said for “can you shoot well enough to notice a change in 10 fps?”

10fps. How do you deal with the reality that any given shot has an ES of over 10fps?

There’s a reason people line up to shoot their rifles over the AB Doppler at matches to get a Custom drag profile from their rifle with their lot of bullets.

Yes- because people delude themselves into believing that every little insignificant detail is the magical reason why they are missing 2 MOA targets- not that they suck and should learn to shoot more. Beyond that, most people into LR shooting are nerds that fancy themselves engineers, and like numbers.

BC fluctuates. Rifling engraving profiles from different barrel manufacturers, lot numbers of bullets. It can all have a measurable effect on BC.

How much in your experience with Doppler radar does BC change rifle to rifle?

This is a proven concept that Brian Litz has scientifically proven.

“Scientifically” proven?

Is it the largest factor in the equation for an hunting rifle in hunting scenarios? Absolutely not. But it can’t be dismissed that the BC number printed on a box of bullets can’t be treated as the gospel when it has been proven that they can vary.

“Real”, actually measured BC numbers do not change rifle to rifle enough to be seen on target that a shooter could positively identify as the cause; unless lot to lot variation of the bullets is so bad that they are functionally different bullets.