Ab app help?

[ubet]

I have ab, and I can’t seem to load my data in correctly to get a decent result. I used their paid for drag models in 77gr smk and 175gr smk. Using a magnetospeed v3 I got my velocities, the 175s were es of 8 sd 3.4 over 10 shots.
I enter all my data, temp elev, humidity, alt, velocity into ab for the bullet profile. I click for solution and it’s saying my mv is over 200fps higher at the muzzle. it was 84f when I did my zero, and now it’s 19f.
The real problem though is with the 77smk data for my ar. It’s saying my velocity at the muzzle is 483 at 19f over the magnetospeed on the same day it was 2280 (ar pistol). Data is entered the same.
What am I doing wrong for it to be giving such wrong info especially for the 77s?

 

[locotrician]

I have the same issue with the velocity calibration , over 200 fps difference on several loads that shot great, im sure in putting something in wrong but i can't figure it out , same with paid curves and just entered bullet info manually.

 

[ubet]

We can’t be the only two this affects

 

[DocUSMCRetired]

How far are you shooting for the calibration?

 

[ubet]

How far are you shooting for the calibration?

I didn’t calibrate it yet. Short on primers etc
But here are screenshots of what I’m talking about. The velocity is showing 1000fps less roughly at the muzzle

 

[_Windrider_]

I didn’t calibrate it yet. Short on primers etc
But here are screenshots of what I’m talking about. The velocity is showing 1000fps less roughly at the muzzleView attachment 7543647View attachment 7543645View attachment 7543646

Look at your MV per degree variation....40 fps. Your MV is 2660 at 70 degrees. You zeroed at 84 degrees.......40x14= 560 FPS error right there.

inalso have to question the pressure in the zero atmosphere. 3200 foot elevation and 84 degrees is impossible for a 29.92 station pressure...looks more like a barometric pressure to me.

 

[ubet]

Look at your MV per degree variation....40 fps. Your MV is 2660 at 70 degrees. You zeroed at 84 degrees.......40x14= 560 FPS error right there.

inalso have to question the pressure in the zero atmosphere. 3200 foot elevation and 84 degrees is impossible for a 29.92 station pressure...looks more like a barometric pressure to me.

I zeroed it and ran the mv at 84 degrees. So should the powder temp be 84?
Here is a screenshot of it changed to 84f and at the current weather. It’s saying the bullet is leaving the barrel at 907fps. No way that can be right

 

[_Windrider_]

I zeroed it and ran the mv at 84 degrees. So should the powder temp be 84?
Here is a screenshot of it changed to 84f and at the current weather. It’s saying the bullet is leaving the barrel at 907fps. No way that can be rightView attachment 7543704

Ideally powder temp should equal ambient temp, ie don’t leave your ammo cooking in the sun.

for your zero atmosphere, are you using a kestrel? Where are you acquire the environmental? It still doesn’t jive. Elevation and station pressure and temp do not jive at all. The elevation looks like DA, pressure looks barometric not absolute. That needs to be revisited. We should start there. When that is correct we can go to step 2 Which would be assuring the ammunition data is correct.

eta, as doc says zero atmosphere not really critical. But what was the temp you used for current environment when getting this error?I bet if you took 70- that temp and multiplied by 40 you’d find the issue.

 

[DocUSMCRetired]

You also do not need to use zero atmosphere for a 100 yard zero. That is for long range zeros.

 

[ubet]

Ideally powder temp should equal ambient temp, ie don’t leave your ammo cooking in the sun.

for your zero atmosphere, are you using a kestrel? Where are you acquire the environmental? It still doesn’t jive. Elevation and station pressure and temp do not jive at all. The elevation looks like DA, pressure looks barometric not absolute. That needs to be revisited. We should start there. When that is correct we can go to step 2 Which would be assuring the ammunition data is correct.

eta, as doc says zero atmosphere not really critical. But what was the temp you used for current environment when getting this error?I bet if you took 70- that temp and multiplied by 40 you’d find the issue.

I compared the data for the nearby airport and when I hit load station atmosphere. I went with data at airport. They were both similar though. My elevation is msl not da, barometric was pulled straight from the local airport reading.
We moved 18mths ago and can’t seem to find my kestrel.

 

[_Windrider_]

I compared the data for the nearby airport and when I hit load station atmosphere. I went with data at airport. They were both similar though. My elevation is msl not da, barometric was pulled straight from the local airport reading.
We moved 18mths ago and can’t seem to find my kestrel.

Barometric pressure is very different than station pressure. Barometric is corrected for sea level. It’s what we use in airplanes. If you are going to use the airport data, don’t use the absolute pressure toggle. See if that makes a difference. Also check that FPS per degree. It’s wrong. Also as doc said, turn off zero atmosphere.

 

[ubet]

So I should be using station pressure then with absolute pressure toggle on?
Zero atmosphere is turned off.
where do I find the FPS per degree?

 

[ubet]

I’m not trying to be dense. Thank you for your patience

 

[_Windrider_]

So I should be using station pressure then with absolute pressure toggle on?
Zero atmosphere is turned off.
where do I find the FPS per degree?

Before I answer, where do u shoot?

 

[Cosmic338]

I have ab, and I can’t seem to load my data in correctly to get a decent result. I used their paid for drag models in 77gr smk and 175gr smk. Using a magnetospeed v3 I got my velocities, the 175s were es of 8 sd 3.4 over 10 shots.
I enter all my data, temp elev, humidity, alt, velocity into ab for the bullet profile. I click for solution and it’s saying my mv is over 200fps higher at the muzzle. it was 84f when I did my zero, and now it’s 19f.
The real problem though is with the 77smk data for my ar. It’s saying my velocity at the muzzle is 483 at 19f over the magnetospeed on the same day it was 2280 (ar pistol). Data is entered the same.
What am I doing wrong for it to be giving such wrong info especially for the 77s?

I only came here to LOL at your profile picture.

 

[ubet]

Before I answer, where do u shoot?

Im in south central Montana

 

[ubet]

I only came here to LOL at your profile picture.

When I first used uploaded it in 2010ish the finger would rub and the eye lid would flick open. lol

 

[_Windrider_]

Im in south central Montana

So elevation of 3200 is accurate?

 

[_Windrider_]

So I should be using station pressure then with absolute pressure toggle on?
Zero atmosphere is turned off.
where do I find the FPS per degree?

Reference post 5 picture 3. See where it says MV Variation? You have it set to 40 FPS/ degree and the velocity you have set is 2260 at 70 degrees. Assuming your problem occurred recently and I’m sure it’s Dick shriveling cold in Montana right now this is your problem. If you were shooting in temps around 20 degrees, this would cause a 2000 FPS error. At 40 degrees it would be 1200 FPS. you get the point. On this page, make sure your environmental conditions are accurate

in the atmosphere section, put in your elevation and pressure you got from the local airport. The pressure is absolute toggle should be OFF. Put in temp and just leave humidity at 50. I’m willing to bet this fixes your issue.

 

[Nik H]

There are a number of incorrect entries here

1. Enter MV as read by your Chronograph
2. MV variation should be more like 0.5 fps/deg or leave it set to zero unless you have actual data.
3. Turn off enable zero atmosphere. Your zero is at 100 yards.
4. There is NO way your station pressure is 29.92 @ 3,200 feet...NO WAY. Either enter Station Pressure (uncorrected) from a Kestrel and turn on pressure is absolute OR enter barometric pressure from a weather app AND the altitude at your location. You NEVER enter a SP with an altitude. Turn off pressure is absolute if entering barometric and altitude.

Just correcting items 2-4 will get you close to where you want to be.

 

[ubet]

Reference post 5 picture 3. See where it says MV Variation? You have it set to 40 FPS/ degree and the velocity you have set is 2260 at 70 degrees. Assuming your problem occurred recently and I’m sure it’s Dick shriveling cold in Montana right now this is your problem. If you were shooting in temps around 20 degrees, this would cause a 2000 FPS error. At 40 degrees it would be 1200 FPS. you get the point. On this page, make sure your environmental conditions are accurate

View attachment 7544215
in the atmosphere section, put in your elevation and pressure you got from the local airport. The pressure is absolute toggle should be OFF. Put in temp and just leave humidity at 50. I’m willing to bet this fixes your issue.

I DIDN’T CATCH THE DEGREE PART!!! I thought it was what my muzzle velocity was varying in the string of shots! I put that to zero, turned off zero atmosphere as well. Our humidity is all over the place here. It’ll be 100 one day and 12 the next sometimes. I did what you said and now it’s fixed. Thanks again, I owe you a beer!

 

[_Windrider_]

I DIDN’T CATCH THE DEGREE PART!!! I thought it was what my muzzle velocity was varying in the string of shots! I put that to zero, turned off zero atmosphere as well. Our humidity is all over the place here. It’ll be 100 one day and 12 the next sometimes. I did what you said and now it’s fixed. Thanks again, I owe you a beer!

Humidity is essentially meaningless Until you get into the 1k-1.5k plus ranges. Leave it at 50% and never change it. Any error from humidity factor is cut in half. Just be sure you are using the correct pressure and setting, otherwise your drops will be wrong.

 

[ubet]

Ok, so I am restarting this necro thread of mine.

I went out and zeroed in a new bullet for an ar15. 62gr hpbt .27bc magneto speed before had said 2950fps. I zeroed at 100 yds, went to 156 with a 3deg up, 275 yds 2 deg, 382yds 1deg. At 156 I was 1.1" high, 275yds I was 9.5" low, 382yds 26.5" low. I converted it into moa, and ran it through muzzle velocity correction in ab, it came out with 2950fps. So, I then put the actual data into ab, and it came back with the holds as 0.5, 2.7, 5.4. The actual data is different, -.674 moa, +3.299moa, +6.26moa. What am I doing wrong? I attached a screenshot of my zero page from the ab app. Any help is appreciated. Thanks

ETA also attached weather from an airport 17 miles to the south for reference at the time of shooting. The farthest I plan to take this load is maybe 500yds, it is a plinking round and for use on prairie dogs around the house.

 

[6.5SH]

Ok, so I am restarting this necro thread of mine.

I went out and zeroed in a new bullet for an ar15. 62gr hpbt .27bc magneto speed before had said 2950fps. I zeroed at 100 yds, went to 156 with a 3deg up, 275 yds 2 deg, 382yds 1deg. At 156 I was 1.1" high, 275yds I was 9.5" low, 382yds 26.5" low. I converted it into moa, and ran it through muzzle velocity correction in ab, it came out with 2950fps. So, I then put the actual data into ab, and it came back with the holds as 0.5, 2.7, 5.4. The actual data is different, -.674 moa, +3.299moa, +6.26moa. What am I doing wrong? I attached a screenshot of my zero page from the ab app. Any help is appreciated. Thanks

ETA also attached weather from an airport 17 miles to the south for reference at the time of shooting. The farthest I plan to take this load is maybe 500yds, it is a plinking round and for use on prairie dogs around the house.

Likely a few small errors in input data that are adding up.

First two I can see are ICAO for the atmospheric standard and G7. I'm guessing the 62 gr HPBT is a Hornady based on the 0.270, but that is a G1 not G7 value and was measured with the ASM standard not ICAO. Change those two items and will get closer to reality.

The others to check are that sight height is correct and that your 100 yard zero is REALLY 100 yards. If it is 92 or 108 yards instead then change that as well. A cheap 300 foot tape reel is a nice thing to have.