Range Report Trying to build a table from my data but nothing lines up

[StampCreek]

Hey gang.

When I shot for the first time last week I had no dope on the gun. A .308 with 175gr SMK gives us a place to start so we knew about where it should hit. Made my hits and recorded the data. After I got home I tried using this data to build a table but tweeking things like MV or scope height I can get either correct up close and way off far away or right on at 1000 yards and way off up close. Used Ballistics AE on my iPad, JBM website and Applied Ballistics website. EVERY site has me at .6 mils at 200 yards. I shot .4 mils. This is with good environmental data. I tried adjusting MV to get me within .1mRAD on the closer targets and then used the truing function to fix the curve but it would throw off everything else.

Now, I know the bullet tells the truth, but I would like to get some kind of table built to have a base line to be able to build off. Otherwise I'm just guesing next time.

Here's all my data, you can plug it into the websites yourself and see what comes up.

Density altitiude 4184' (2441' elevation, 29.91"Hg, 75 degrees, 38% relative humidity)
175gr SMK
G1 drag info used
All known distance targets
Winds right to left all day, full value to half value as they moved around. 8-16mph winds (I know a right crosswind will cause the impacts to rise but can't imagine it's this much of a disparity)
100 yard zero confirmed on site, all shots done using just holdover with an H59 reticle

Yards mRAD
200 .4
300 1.2
400 2.0
525 3.2
600 4.1
775 6.3
800 6.9
900 8.4
1000 10.5
1100 12.2

We shot up to 1100 yards and then took a break, then started at 1000 and came back down to double check the data and make some corrections. 400 yards went from 2.3 to 2.0. 600 yards 4.3 to 4.1. 800 yards 7.2 to 6.9. 900 yards 8.2 to 8.4.

Feel like I'm chasing my own tail here. Just can't get a table to come close enough to what happened to have something to work off. Any ideas would be appreciated.

 

[MitchK]

It could be your scope adjustments are a little off. Or it could be that the distance to the target is a little off

 

[StampCreek]

It could be your scope adjustments are a little off. Or it could be that the distance to the target is a little off

No scope adjustments, all holds. Ranges all known and verified with a LRF.

The last Ballisitc for iPad I ran with good environmental data and it has me right on at 1100 and 1000 with increasing errors as we go shorter. Tried truing it but throws everything off. I figured the table would be close or right on at the shorter ranges and I'd have to true it for the long range. Couldn't fit it all on the screen. 800 yards shows 7.1 mRad and 900 8.6.

 

[StampCreek]

Oh, just to add. We did a trajectory ranging exercise where I shot at an unknown (to me) distance target, walked my fire to the target, made my hit, and then using that hold data figured it's range. So my confidence is high for known ranges and mil hold data.

Could be a variety of things going on here I know. Just seeing if I'm missing something silly and easy. I appreciate the input.

 

[_Windrider_]

If I were to guess, iits the DA throwing off the results. How did you get your environmentals? Try using absolute pressure and temp. You wiill get better results. I have found that when trying to use DA in the field, i dont get good results. In my most minimal experince, nothing beats using actual data measured from my Kestrel. I also use Ballistic AE and its rarely far off from what JBM will give me or Shooter.

 

[StampCreek]

If I were to guess, iits the DA throwing off the results. How did you get your environmentals? Try using absolute pressure and temp. You wiill get better results. I have found that when trying to use DA in the field, i dont get good results. In my most minimal experince, nothing beats using actual data measured from my Kestrel. I also use Ballistic AE and its rarely far off from what JBM will give me or Shooter.

Interesting.

While I didn't catch on at the time, the instructor (Dan Newberry @ Bangsteel) had JBM website up on his iPhone and he was getting way closer data to what I was actually shooting than I was as shown above. So it must be an environmental this. Question now is....how to fix it.

How I got the environmentals in this case was actually using the app feature to grab local weather data and plug into the app. Kestrel hasn't shown yet

However, I know the range elevation, temp that day and humidity can be set to 50%. Only variable would be the barometric pressure which was grabbed from local weather. Obviously I can play with that number and see what happens to my chart.

Thanks.

 

[_Windrider_]

Interesting.

While I didn't catch on at the time, the instructor (Dan Newberry @ Bangsteel) had JBM website up on his iPhone and he was getting way closer data to what I was actually shooting than I was as shown above. So it must be an environmental this. Question now is....how to fix it.

How I got the environmentals in this case was actually using the app feature to grab local weather data and plug into the app. Kestrel hasn't shown yet

However, I know the range elevation, temp that day and humidity can be set to 50%. Only variable would be the barometric pressure which was grabbed from local weather. Obviously I can play with that number and see what happens to my chart.

Thanks.

Problem is you have no idea where its actually pulling data from. You could be in the Smokies somewhere and its getting its data froma nearby weather station, likely a HIWAS equipped VOR station nearby or an airport with weather measuring and reporting equipment. trying putting in 27.42 as your barometric pressure (make sure pressure is set to absolute) and your temp of 75. I leave humidity at 50% and never touch it. See what that does, Im just curious. But when you get that Ketsrel, you will have much better luck.

 

[StampCreek]

Problem is you have no idea where its actually pulling data from. You could be in the Smokies somewhere and its getting its data froma nearby weather station, likely a HIWAS equipped VOR station nearby or an airport with weather measuring and reporting equipment. trying putting in 27.42 as your barometric pressure (make sure pressure is set to absolute) and your temp of 75. I leave humidity at 50% and never touch it. See what that does, Im just curious. But when you get that Ketsrel, you will have much better luck.

Did it. Didn't make a big difference. Dropped the baro to 20" absolute and the shorter range number started getting closer but the 1000 yard number was now off by a mil.

Funny, his data had me .4 mils at 200 yards to confirm the zero. I saw his iPhone screen with my own eyes. I can't get anything less than .6 without rocketing the MV and then everything else is junk. Weeeeeird.

Also tried variations of MV and scope height with no luck. Guess I need the Kestrel and to go back and shoot more. Still, I wish I could make sense of the data I've got.

 

[_Windrider_]

Whats your assumed MV?

 

[StampCreek]

2650

 

[StampCreek]

What MitchK said is stuck in my head. Maybe the distances are just a little off. Most everything out to 800 is about 25 yards off.

Maybe a combination of a couple yards, just a few, and a bad baro setting. I dunno.

 

[Lowlight]

What type target were you shooting and what did you use to confirm distance from POA to POI ?

Your numbers are all about .2 fast for a 175 so it's going pretty fast or the ranges are off, or your POA is not 100% true with your POI.

Usually its 1.5, 2.2, 3.5, etc. so you're trending quicker than normal. Your MV would help.

 

[_Windrider_]

What MitchK said is stuck in my head. Maybe the distances are just a little off. Most everything out to 800 is about 25 yards off.

Maybe a combination of a couple yards, just a few, and a bad baro setting. I dunno.

Using your MV and some general assumes (swags) this is what I got using your MV and a 175grain HPBT MK

Posted via Tapatalk HD for iPad

 

[StampCreek]

What MitchK said is stuck in my head. Maybe the distances are just a little off. Most everything out to 800 is about 25 yards off.

Maybe a combination of a couple yards, just a few, and a bad baro setting. I dunno. The only one I can check right now is the 400 yard distance. I can easily see that spot on google earth and my shooting position to there is right on. Fwiw

 

[StampCreek]

What type target were you shooting and what did you use to confirm distance from POA to POI ?

Your numbers are all about .2 fast for a 175 so it's going pretty fast or the ranges are off, or your POA is not 100% true with your POI.

Usually its 1.5, 2.2, 3.5, etc. so you're trending quicker than normal. Your MV would help.

Various steel targets. Large squares or silhouettes. Smallest was a 12x12 at 800 yards.

Ranges- it's his range and his backyard. Honestly I went with that. I shot a couple with my Swarovski LRF just to see if it worked (just bought it).

Seems way way too fast to be a hot MV. I'm leaning towards distances being slightly off.

Sure helps to be able to talk to someone about this and bounce ideas around. Thanks!!

 

[Lowlight]

If you're only off by .1 at 200 I would just trend the software to be right further out, it's pretty irrelevant at 200, a 1/2 MOA group is bigger than the margin of error.

Worry thy about the longer ranges being right.

 

[Lowlight]

If you use steel you need a watermark across the center so you can hold the reticle consistently as well as being able to determine the distance above or below center.

Steel can hide a lot of variations, certainly more than .2 mils when you're talking a 2 to 4MOA target.

25 yards at 400 yards is .2 alone.

 

[StampCreek]

If you use steel you need a watermark across the center so you can hold the reticle consistently as well as being able to determine the distance above or below center.

Steel can hide a lot of variations, certainly more than .2 mils when you're talking a 2 to 4MOA target.

25 yards at 400 yards is .2 alone.

They all had a cross or circle to aim at and fine tune. I could aim 3 o'clock on the circle as a finer point of aim. Worked pretty good.

 

[StampCreek]

If you're only off by .1 at 200 I would just trend the software to be right further out, it's pretty irrelevant at 200, a 1/2 MOA group is bigger than the margin of error.

Worry thy about the longer ranges being right.

With my environmental data now I'm .2 off at 200 and right on at 1000. Not a deal breaker I guess.