Do you adjust MV or BC value of a ballistic app when field proven the ballistics?

[Elite]

Hello everyone,

I will be verifying my ballistic data today and extended ranges, I am wondering if everyone adjusts the MV to match the real world data or the bullets BC value?

MV seems like the most reliable way but if I have to slow the MV down that would shorten the effective range vs the actual BC value being off


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[Shortschaf]

Adjust the one you have least confidence in.
That means:

• If you have chronograph data, adjust BC
• If you don't have chronograph data, adjust speed

This is a decent video to explain

Re posting this because of its importance

www.longrangehunting.com

I have a chronograph, and I use what Applied Ballistics library tells me for BC, and I haven't had to "true" either one yet.

Please note that "truing" anything requires that you have the atmospherics correctly entered. That is an extremely common error people make

 

[Hydra6]

I true the muzzle velocity at 600 and true BC for 800 yards (or more). This is with my Kestrel with AB.

 

[inkedspot]

I true the muzzle velocity at 600 and true BC for 800 yards (or more). This is with my Kestrel with AB.

^^^^ This

 

[Tnc]

Hydra6 is correct.

 

[manitou1]

Everything I have read is true MV to 600 and BC beyond that.

If you look at Hornady's website they give three BCs for each of their bullets. BCs change as velocity changes so this makes sense... and works.

 

[Antares]

Hydra6 is correct.
View attachment 743313

Slow your roll, new guy. If you're gonna meme on day 1, it had better be hilarious.

 

[Shortschaf]

Sorry, fixed my link above

 

[Tnc]

Slow your roll, new guy. If you're gonna meme on day 1, it had better be hilarious.

I thought it was hilarious

 

[Elite]

I true the muzzle velocity at 600 and true BC for 800 yards (or more). This is with my Kestrel with AB.

Thanks, So do you just dial to what the apps says then shoot at 600 and measure the difference?


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[Fetty Wapiti]

I do this daily, if using a truly good chrono like a xero always true your BC. No matter the range. start your true at 500 then move it out. Run a doppler BC if possible not a G7

 

[NSI]

I always used to "fix" the MV using a Chrono since it was "known" and mess with the BC to true.

Following S2HU, I true using MV based on confirmed drops on a truing target at range. @Formidilosus taught that MV variance is minimal from most bullet makers, and is generally reported correctly.

-J

 

[manitou1]

Thanks, So do you just dial to what the apps says then shoot at 600 and measure the difference?


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Calculate your ballsitics.

Shoot at say 500-600. Observe where you hit, then compare it to your ballistic caculator range card drops. Adjust the calculator to represent the new velocity value that matches your actual drop.

Beyond 600 yards do the same, but instead of adjusting your velocity, change your bc in your calculator until it matches your drop.

I hope this made sense.

 

[Shortschaf]

I always used to "fix" the MV using a Chrono since it was "known" and mess with the BC to true.

Following S2HU, I true using MV based on confirmed drops on a truing target at range. @Formidilosus taught that MV variance is minimal from most bullet makers, and is generally reported correctly.

-J

So you would change the one thing you can measure, and affix the one thing bullet manufacturers lie/inflate the most?

 

[NSI]

So you would change the one thing you can measure, and affix the one thing bullet manufacturers lie/inflate the most?

I understand the reluctance. It doesn’t make much sense as I explain it.

Perhaps Form or @PNWGATOR can tag in with the more detailed rationale. As I understand it, one needs a substantial mod to BC in most cases to true with it, and such large changes are outside the scope of variance for BC.

-J

 

[Fetty Wapiti]

Everything I have read is true MV to 600 and BC beyond that.

If you look at Hornady's website they give three BCs for each of their bullets. BCs change as velocity changes so this makes

I understand the reluctance. It doesn’t make much sense as I explain it.

Perhaps Form or @PNWGATOR can tag in with the more detailed rationale. As I understand it, one needs a substantial mod to BC in most cases to true with it, and such large changes are outside the scope of variance for BC.

-J

That is why we true/tune mv first in most cases, however, with a good muzzle velocity measurement you are only trueing the velocity to average out an equation in a sense; think about manipulating a number to get a better solution that is not exact, without putting in the time to realize if you modified the right input you would have a true solution. Making things better don't always make things great.

If you have a solid MZ velocity run it to 500 and true BC. If this works, run 800 and true again.

If that doesn't work start looking at other factors that you didn't take into account like poi offset, powder temp and factor (don't trust manufactures), and spin drift... just to get the list started.

 

[Formidilosus]

BC variation is within 10-15 points for every bullet I have seen fired from multiple rifles using Doppler and Oehler 89’s, unless there is something very wrong. Given a good bullet, the BC given is generally spot on. If you are shooting a Hammer, then yeah- the BC is wrong.

A 10 point difference in a .536 G1 BC (.536 vs. .546) bullet at 800 yards with a 2,940 fps MV is a whopping 1.2 inches- thinner than half the crosshairs on lots of scopes.

148.9”


147.7”.





So you guys actually believe you can discern a 1 inch difference at 800 yards in group vertical location? A single click of the turret is more than that.


People messing with known BC values are mind jerking themselves believing that they are shooting inside of, and can actually positively detect a 1” shift at 800 yards due BC variation, and not the fact that you aren’t actually zeroed to less than .1 mil at 100 yards, not shooting enough shots over a chrono to actually see the real average MV, nor shooting enough shots at 800 yards to form a real group (20-30 shots group size) in order to positively detect a 1 inch difference in elevation, or reading wind to within .5 mph for upset/downdraft, etc., etc, etc.

 

[Elite]

Calculate your ballsitics.

Shoot at say 500-600. Observe where you hit, then compare it to your ballistic caculator range card drops. Adjust the calculator to represent the new velocity value that matches your actual drop.

Beyond 600 yards do the same, but instead of adjusting your velocity, change your bc in your calculator until it matches your drop.

I hope this made sense.

That does make sense and will go that route. How come 600 is the number for changing the BC value?


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[Elite]

BC variation is within 10-15 points for every bullet I have seen fired from multiple rifles using Doppler and Oehler 89’s, unless there is something very wrong. Given a good bullet, the BC given is generally spot on. If you are shooting a Hammer, then yeah- the BC is wrong.

A 10 point difference in a .536 G1 BC (.536 vs. .546) bullet at 800 yards with a 2,940 fps MV is a whopping 1.2 inches- thinner than half the crosshairs on lots of scopes.

148.9”
View attachment 743512

147.7”.
View attachment 743517




So you guys actually believe you can discern a 1 inch difference at 800 yards in group vertical location? A single click of the turret is more than that.


People messing with known BC values are mind jerking themselves believing that they are shooting inside of, and can actually positively detect a 1” shift at 800 yards due BC variation, and not the fact that you aren’t actually zeroed to less than .1 mil at 100 yards, not shooting enough shots over a chrono to actually see the real average MV, nor shooting enough shots at 800 yards to form a real group (20-30 shots group size) in order to positively detect a 1 inch difference in elevation, or reading wind to within .5 mph for upset/downdraft, etc., etc, etc.

Thanks for great info. This is a very good point and seems like trueing MV is the option. I don’t plan to shoot at game past 500 anyways. But like to play at the range out to 1000


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[Shortschaf]

BC variation is within 10-15 points for every bullet I have seen fired from multiple rifles using Doppler and Oehler 89’s, unless there is something very wrong. Given a good bullet, the BC given is generally spot on. If you are shooting a Hammer, then yeah- the BC is wrong.

A 10 point difference in a .536 G1 BC (.536 vs. .546) bullet at 800 yards with a 2,940 fps MV is a whopping 1.2 inches- thinner than half the crosshairs on lots of scopes.

148.9”
View attachment 743512

147.7”.
View attachment 743517




So you guys actually believe you can discern a 1 inch difference at 800 yards in group vertical location? A single click of the turret is more than that.


People messing with known BC values are mind jerking themselves believing that they are shooting inside of, and can actually positively detect a 1” shift at 800 yards due BC variation, and not the fact that you aren’t actually zeroed to less than .1 mil at 100 yards, not shooting enough shots over a chrono to actually see the real average MV, nor shooting enough shots at 800 yards to form a real group (20-30 shots group size) in order to positively detect a 1 inch difference in elevation, or reading wind to within .5 mph for upset/downdraft, etc., etc, etc.

So you run straight BC values from the box and just change MV until it lines up?

ETA: how much are you changing MV from chronograph results to get dope to align? 10, 20, 50, up to 100fps?

And who said anything about truing up an inch at 800 yards?