Question on velocity correction

[newgunguy3]

Sorry, newbie question. I have some dope on my rifle and a recently purchased 5700 elite. I plugged in all the variables to generate the gun profile then looked at the proposed ballistic solutions for various distances. The 5700 solutions for elevation are off across the board compared to my dope. So that means I need to use the velocity truing option. Once set, I assume the ballistic solutions should be closer to my dope, correct?

My question is, how do I reset or disregard that velocity setting? For example, I change ammo lot and the chrono indicates the inital velocity is N. Do I just change the velocity value in the gun profile then do more tests to determine new dope and update the muzzle velocity truing based on real-life results?

Thanks

 

[Lowlight]

All manually, you have to put in the work as there is no free lunch.

You would make multiple tracks for different ammo or velocities observed.

 

[Dthomas3523]

Also, are you using the custom curve or g1/g7?

With custom, velocity is all you can mess with (and sight height).

G1/g7, you can change velocity and BC.

 

[DaveM]

Velocity from your chronograph isn’t always going to be correct, and there is no reasonable way to test it’s accuracy. Don’t rely on it as an absolute value. It’s an excellent tool to measure consistency, but it could easily be giving you the wrong speed.

Think of it like trying to measure to .0001 with $50 calipers.

 

[lte82]

Can you post your actual dope vs predicted dope at 300, 600, and somewhere 800-1000?

 

[newgunguy3]

Can you post your actual dope vs predicted dope at 300, 600, and somewhere 800-1000?

I will tonight when I get home and have access to the device. Thanks

 

[theLBC]

any option to load different profiles for different ammo?

 

[blbennett1288]

There is two ways to accomplish this:

1.) Use G1/G7, change the BC, and leave MV alone. I disagree with @DaveM and if you have multiple outings with the same MV. I think it is about as solid as the data is going to get, especially with Magnetospeed V3 or Labradar. I use this method for my 16.75” .308 bbl w/ 168grs and 26” 6BR w/ 105grs

2.) Use one of the custom curves and change MV. Some of the custom curves seem better than others. I know there is about 10-15 options for some. I use this method for 24” 6.5CM w/ 140grs. The Muzzle velocity adjustment to get the .308 and 6BR to line with the custom curve was large enough for me to choose option #1.

Of course verify dope at the longest supersonic distance possible.

 

[Near miss]

Having only touched Kestrels / AB systems surface, I would like to point out that the cdm is after all, the precise bullet path for someone else's gun/barrel!

Also, if you ever try to build a powder temp MV table, which I recommend to get all out of your device, messing and guessing with the MV shown by your chrono is going to drive you nuts.

That said, be prepared to face it that your chrono might have an offset of +/-10 fps or so.

This MV calibration is preferred by AB because in the supersonic range MV has much more effect on trajectory than changes in BC. But maybe in the real world they both have to be played with.

 

[Lowlight]

The MV variations in most modern chronographs like the Magneto and Labradar are not going to cause you to miss a target

Maybe at 1 Mile if you use a 16" Plate you might see a round go past it, but inside 1000 yards, you are talking a minor vertical spread found in most factory loads

This whole BULLSHIT Line of debate that your chronograph is wrong is outdated, if you are using an old piece of shit with sky screens and the sun is ducking in and out of clouds because you don't have an IR Source, okay, you might have a point, but today in 2020 you're MV is not an issue

I can dope my rifle any day of the week, and it will hold true. The elevation is not moving that much unless you are traveling from location to location.

 

[DaveM]

The MV variations in most modern chronographs like the Magneto and Labradar are not going to cause you to miss a target

Maybe at 1 Mile if you use a 16" Plate you might see a round go past it, but inside 1000 yards, you are talking a minor vertical spread found in most factory loads

This whole BULLSHIT Line of debate that your chronograph is wrong is outdated, if you are using an old piece of shit with sky screens and the sun is ducking in and out of clouds because you don't have an IR Source, okay, you might have a point, but today in 2020 you're MV is not an issue

I can dope my rifle any day of the week, and it will hold true. The elevation is not moving that much unless you are traveling from location to location.

Thank you for clearing up any big misconceptions about modern chronos being inaccurate. I have not read or heard anywhere that they had been tested against more expensive and precise speed measurement systems. I never meant to imply that they are wildly inaccurate.

OP didn’t mention how much his dope was off vs his Kestrel solution. Could be inches, could be feet. OP also didn’t mention what he used to get his velocity.

Velocity from a magneto speed or Labradar and a Kestrel should definitely have one making hits on full size IPSC’s past 600 yards right from the start. Mine has been accurate enough for first round hits to 980.

 

[Lowlight]

980 whole yards, or are there a few feet in that value?

Of course they have been up against more precise devices and tested for accuracy, that was done when they first came out

In fact, because Software changes muzzle velocity we don't even bother chronographing students in our precision rifle classes anymore because the software will change the number as that is their one of only two methods to true.

We do drop at 600 yards and back the software into the solution, it's much easier, takes less time, and cuts out the need to chronography completely. Even cheap factory match ammo has an SD under 20fps in most rifles, so again, we are talking a minor vertical spread at extended distances.

Guys are shooting 6.5CMs to 1 Mile and hitting by routine with factory ammo, so your MV is not an issue.

Today with software, unless you don't have a range that goes to 600 yards, you really don't need a chronograph except if you are reloading.

 

[DaveM]

980 whole yards, or are there a few feet in that value?

Of course they have been up against more precise devices and tested for accuracy, that was done when they first came out

In fact, because Software changes muzzle velocity we don't even bother chronographing students in our precision rifle classes anymore because the software will change the number as that is their one of only two methods to true.

We do drop at 600 yards and back the software into the solution, it's much easier, takes less time, and cuts out the need to chronography completely. Even cheap factory match ammo has an SD under 20fps in most rifles, so again, we are talking a minor vertical spread at extended distances.

Guys are shooting 6.5CMs to 1 Mile and hitting by routine with factory ammo, so your MV is not an issue.

Today with software, unless you don't have a range that goes to 600 yards, you really don't need a chronograph except if you are reloading.

980 yards ranged with Sig BDX3k. I was pleasantly surprised.

I agree on all other points.

 

[newgunguy3]

Can you post your actual dope vs predicted dope at 300, 600, and somewhere 800-1000?

I will tonight when I get home and have access to the device. Thanks

Okay, here we go. I'm shooting Prime 175 gr 308. The ammo is several years old (Ruag manufacturer). According to Magnetospeed V.3, the MV is 2656 which is what I put into the gun profile in the 5700 elite. I know it's just an estimate and may not be 100% accurate but it's a starting place. I'm using AB's custom BC for the SMK 175 projectile. The kestrel has the latest (1.35) version of firmware.

Here's my dope and Kestrel solutions (in mils):

distance dope kestrel
300 yds 1.2 1.22
600 yds 4.0 4.37
650 yds 4.7 5.02
700 yds 5.2 5.71
750 yds 6.0 6.44

Thanks for your insights.

 

[Dthomas3523]

980 whole yards, or are there a few feet in that value?

Of course they have been up against more precise devices and tested for accuracy, that was done when they first came out

In fact, because Software changes muzzle velocity we don't even bother chronographing students in our precision rifle classes anymore because the software will change the number as that is their one of only two methods to true.

We do drop at 600 yards and back the software into the solution, it's much easier, takes less time, and cuts out the need to chronography completely. Even cheap factory match ammo has an SD under 20fps in most rifles, so again, we are talking a minor vertical spread at extended distances.

Guys are shooting 6.5CMs to 1 Mile and hitting by routine with factory ammo, so your MV is not an issue.

Today with software, unless you don't have a range that goes to 600 yards, you really don't need a chronograph except if you are reloading.

Yep. Late last year I started only using chrono for load development. And sometimes when a barrel has high round count.

I have found that inputting whatever muzzle velocity the software needs is far less stressful than trying to make it all work around my known MV.

 

[lte82]

Since your 300 yard dope is spot on I would call your zero good.

What jumps out at me is that you need +.7 mil from 600 to 650 but only +.5 mil from 650 to 700, then +.8 from 700 to 750. IMO either your target distances are not accurate or your scope may be having issues. It sounds like you are doing everything right, I don’t think tweaking velocity or bc is going to fix the problem... Do you have another scope to try?

 

[_Windrider_]

Okay, here we go. I'm shooting Prime 175 gr 308. The ammo is several years old (Ruag manufacturer). According to Magnetospeed V.3, the MV is 2656 which is what I put into the gun profile in the 5700 elite. I know it's just an estimate and may not be 100% accurate but it's a starting place. I'm using AB's custom BC for the SMK 175 projectile. The kestrel has the latest (1.35) version of firmware.

Here's my dope and Kestrel solutions (in mils):

distance dope kestrel
300 yds 1.2 1.22
600 yds 4.0 4.37
650 yds 4.7 5.02
700 yds 5.2 5.71
750 yds 6.0 6.44

Thanks for your insights.

What’s the BC on the box and at what speed?

i have more questions but let’s start there

 

[wade2big]

980 whole yards, or are there a few feet in that value?

Of course they have been up against more precise devices and tested for accuracy, that was done when they first came out

In fact, because Software changes muzzle velocity we don't even bother chronographing students in our precision rifle classes anymore because the software will change the number as that is their one of only two methods to true.

We do drop at 600 yards and back the software into the solution, it's much easier, takes less time, and cuts out the need to chronography completely. Even cheap factory match ammo has an SD under 20fps in most rifles, so again, we are talking a minor vertical spread at extended distances.

Guys are shooting 6.5CMs to 1 Mile and hitting by routine with factory ammo, so your MV is not an issue.

Today with software, unless you don't have a range that goes to 600 yards, you really don't need a chronograph except if you are reloading.

But when I say it nobody cares. ?

I never understood the draw of the chronographs. They are a tool and thats it. One I don’ need. A man can learn all he needs with the target alone. The target and a free ballistic app is better and easier though.

Since I have been target shooting, i always trued like you said. I would actually shoot every hundred yards and verify because it’s good practice and I have the space and my own range. I do use a free app and move the muzzle velocity until my numbers line up.

 

[newgunguy3]

Answering your questions

The box information (G1, G7, drag etc.) is almost identical to the information posted for the ammunition today at the bottom of this page: https://www.primeammo.com/ammunition/308/prime-308-win-otm-175gr-match-case.html There are some slight differences in the trajectory (inch) table. My box says

distance 100 yds 200 yds 300 yds 500 yds 800 yds 1000 yds
100 yd zero x -4.93 -15.49 -57.29 -191.76 -352.88
300 yd zero 5.01 5.12 x -32.15 -151.55 -302.62
500 yd zero 11.3 17.69 18.45 x -101.29 -239.77


As far as another scope because the mill delta amount changes at different distances, yes, I do have another. In fact on this rifle I just changed from a Burris XTRII 5-25 to the Burris XTRIII 5.5-30 both FFP. I have done several ladder tests and box drills on the XTRII and it was always spot on.

I'm taking this gun with the new scope out to stretch its legs in a couple of weeks which is what prompted the 5700 elite purchase. But I wanted to see how the Kestrel compared to my dope. When I noticed the differences it prompted my original question.

Thanks again.

 

[C_R_Slacker]

Download a ballistic app to your phone and see if it spits out the same solution as your kestrel (make sure environmental info is the same between the two). Sometimes the phone apps are easier to manipulate numbers than kestrels are.

 

[seansmd]

Okay, here we go. I'm shooting Prime 175 gr 308. The ammo is several years old (Ruag manufacturer). According to Magnetospeed V.3, the MV is 2656 which is what I put into the gun profile in the 5700 elite. I know it's just an estimate and may not be 100% accurate but it's a starting place. I'm using AB's custom BC for the SMK 175 projectile. The kestrel has the latest (1.35) version of firmware.

Here's my dope and Kestrel solutions (in mils):

distance dope kestrel
300 yds 1.2 1.22
600 yds 4.0 4.37
650 yds 4.7 5.02
700 yds 5.2 5.71
750 yds 6.0 6.44

Thanks for your insights.

That's good, now in the profile adjust the MV and look at the 600 and try and kind them up. Your closer dope should stay true.

Then when you get out to 800+ if it starts to diverge adjust the BC and kind up that part of the curve.

As Frank said if you use different ammo create a different profile, rinse and repeat.