Truing ballistic app

[DLT]

I have been using geo ballistics for a little while now for 6 creedmoor. Most if not all days it has been spot on. I decided to upgrade the account so I could add my 223. Shooting a known distance, I entered in all the information down to the letter. Atmospheric conditions, wind, angle, chrono data, sight height, the off sets, and anything else I had data on. It called for 19 moa. I got on target finally at 17 moa. I have had to fudge numbers before to make other apps come out right but this one is way off. Do I fudge the numbers such as bullet bc and velocity to make it work ?

 

[WSnyder]

Do I fudge the numbers such as bullet bc and velocity to make it work ?

Yes, this is common. Typically it’s recommended to change velocity first to true out to say 500 yds and then fine tune bc with yardages out at 800-1000. Before doing this I’d double check all of your inputs to make sure they are correct before truing if you think it’s too far off to start with.

 

[CharlieNC]

Continue to collect data from multiple shooting sessions to determine the average drops at distances and the average conditions to achieve the best adjustments to make. Differences in mirage, unknown wind, etc which affects individual results will be averaged out .

 

[tydaws]

Below is a link to Precision Rifle Blog. It contains information about how 2-time PRS champion Austin Orgain trues his data, specifically manipulating MV & BC. I've not yet put this method to work, but there is quite a lot of experience & success speaking here.

How A 2-Time PRS Champ Trues His Ballistics & Calculates His Dope At A Match – Austin Orgain Spotlight Part 3

This article is part of a series that is taking a deep dive with 6 of the most dominant precision r...

precisionrifleblog.com

 

[DLT]

I’m having a rough time getting it to come out. I have only got solid results on paper out to 350 so far.

 

[DLT]

I have decided that my new ballistic app is gonna be my first hit. aka 'sighter'

Mine is gonna be a dope card and hope for the best. Also the barrel is a 8 twist. I’m certain it won’t stabilize the 88eldm. Maybe the 80.5 bergers would though. The rifle is shooting good with the 80smk with only a es of 8fps with 5 shots

 

[FeMan]

As MSnyder said, if every other input is correct, you should get a good ballistic curve if you fudge MV to get the app to line up with drops at 600 and then fudge the BC to get it to line up with impacts at 1k. Make sure everything else is correct though. Pressure/elevation are the most critical inputs with temperature third. If you dont have those right, you will be chasing your tail.

 

[J_idaho]

Mine is gonna be a dope card and hope for the best. Also the barrel is a 8 twist. I’m certain it won’t stabilize the 88eldm. Maybe the 80.5 bergers would though. The rifle is shooting good with the 80smk with only a es of 8fps with 5 shots

You know that using a twist calculator tells you if you have enough twist and If you’re getting the full BC out of your bullet. You might try keeping velocity same and changing BC. I have not tried this because I only shoot bullets that match my twist. Speed has little effect on BC value.
Please post back if you figure out what works to fix it I’m very curious. This is something that is always a debate. I think applied ballistics says you have to be way past 1000 yards to be able to true ballistics. So you’re probably way better off to start at a 1000 and check 600. My kesteral is usually right on.

 

[DLT]

As MSnyder said, if every other input is correct, you should get a good ballistic curve if you fudge MV to get the app to line up with drops at 600 and then fudge the BC to get it to line up with impacts at 1k. Make sure everything else is correct though. Pressure/elevation are the most critical inputs with temperature third. If you dont have those right, you will be chasing your tail.

The geo ballistics app doesn’t have an input for elevation. If I does I have not been able to find it which is crazy

 

[FeMan]

The geo ballistics app doesn’t have an input for elevation. If I does I have not been able to find it which is crazy

The manual for the app says you are supposed to input station pressure and actual temp under "Atmospherics", which is better than elevation but tougher to come up with. Unless you are getting this input correctly for each session your outputs will not be consistent and correct.

 

[Fast14riot]

Use G7bc, also verify scope clicks with a tall target test. Does that app allow velocity bands?

 

[Brians356]

The manual for the app says you are supposed to input station pressure and actual temp under "Atmospherics", which is better than elevation but tougher to come up with. Unless you are getting this input correctly for each session your outputs will not be consistent and correct.

OTOH if it only relied on "Elevation" it would be even less useful.
-

 

[Eagle Six]

As stated the best is to use station pressure and temperature (to a small degree also humidity). From this the calculation for density altitude is more accurate and DA effects and predict the trajectory more accurately.

Unless specified otherwise local weather and airport weather report barometric pressure, which is pressure corrected from sea level. It can be used and often is, but not as accurate.

If you have a Kestrel handheld weather meter or similar, we set the altitude on '0' (zero) and it will display station pressure (also referred to as absolute) where you are standing. It will also provide actual temperature where you are standing. The ballistics calculator then uses density altitude to calculate trajectory.

When using weather stations or airport reporting they usually are miles from where we are shooting. If the weather system is stable a few miles distance from that station it will not have a great effect. However, if it is an unstable weather system, the conditions at the reporting station can be considerably different than where we are standing.

 

[DocUSMCRetired]

The most accurate method is to use Station Pressure and Temperature. Using Density altitude can lead to errors as its less accurate and a generalization of the weather.

You want to true Muzzle Velocity in the super sonic range. You also want to make sure you run a turret tracking test. If your turrets have a slight variation (which a lot of them do, since scopes are generally made on an assembly line) then it is ok to true that out using muzzle velocity or if your app/device allows you can sometimes input that offset. Like you can do in the Garmin, Kestrel, Vectronix etc.

For supersonic trueing you want to adjust Drop Scale Factor, if your app doesn't have that then you can simply tweak the BC but that is only recommended as a secondary option.

 

[DLT]

The most accurate method is to use Station Pressure and Temperature. Using Density altitude can lead to errors as its less accurate and a generalization of the weather.

You want to true Muzzle Velocity in the super sonic range. You also want to make sure you run a turret tracking test. If your turrets have a slight variation (which a lot of them do, since scopes are generally made on an assembly line) then it is ok to true that out using muzzle velocity or if your app/device allows you can sometimes input that offset. Like you can do in the Garmin, Kestrel, Vectronix etc.

For supersonic trueing you want to adjust Drop Scale Factor, if your app doesn't have that then you can simply tweak the BC but that is only recommended as a secondary option.

I am currently using the geo ballistics app. My ranges I have access to are 100-600. Then we have a steel plate set up at 670 and a couple more at 830

Does anyone have the g7 for a 80smk ?

 

[Fast14riot]

80smk G7 0.218BC

 

[DocUSMCRetired]

I am currently using the geo ballistics app. My ranges I have access to are 100-600. Then we have a steel plate set up at 670 and a couple more at 830

Does anyone have the g7 for a 80smk ?

Be careful with close range truing. It adds levels of error that cannot be avoided. Check out this video on the subject:

 

[Forum Boss]

Doc knows his stuff.

I will just add here are some common issues,

1. Scope height above centerline of bore set by default or otherwise incorrectly.

2. Bullet BC is slightly exaggerated by maker, or is wrong in App.

3. Targets at 300 yards and beyond are NOT at same elevation as shooter, even though it appears range is flat.