Ol' Brethren of TexAgs
I'm hopeful that one of you on here are up to speed on long range shooting ballistics and/or the popular Shooter App for your smart phone

Here is my issue: I have dialed in two different rifles (308 and 300 RUM) and each shoot good groups. The 308 has a Krieger barrel and produces a 0.287" group at 100y and the 300 Ultra Mag is right at 0.350" group. I am trying to reach out to 1,000 yards then eventually 1,500, but I'm having a hard time with my shooter app giving me the right MOA adjustments. A few months ago, I shot each gun at 200, 300, 400, 600 and 700 yards. On the 200-400 yard ranges, I kept my MOA at 0 and just measured my bullet drop to see if it would correlate with my Shooter App. Then, on the 600 and 700y distances, I used the Shooter App MOA recommendation, but that only got me close. I then had to tweak it a few more MOA. See me notes below. You will first see what my actual MOA should be, then below that, you will see what the Shooter App tells meand its off by quite a bit.
Anyone have any ideas as to why it's so far off? My velocity was measured with one of those LabRadar deals as well as a chronograph.


308 Krieger Barrel
Scope Measurement (height above barrel) 1.825
Velocity: 2,646 fps. STD 8.4
Below is the true MOA readings:

200 yard Low 5" 2.5 MOA
300 yards Low 16.25" 5.4 MOA
400 yards Low 33.0" 8.25 MOA
600 yards Low 91.5" 15.25 MOA
700 yards Low 140" 20 MOA

The chart below is not accurate for 200 yards, 300 yards, 600 yard and 700 yards
The 400 yard MOA value is correct. Not sure why the values I manually entered are not correct? See below this chart



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300 Remington Ultra Mag
Scope Measurement (height above barrel) 1.824
Velocity: 3,315 fps. STD 17.3

200 yard Low 2" 1 MOA
300 yards Low 6" 2 MOA
400 yards Low 12.75" 3.18 MOA
600 yards Low 45" 7.5 MOA
700 yards Low 70" 10 MOA

The chart below is not accurate for 200 yards, 300 yards, 400 yard and 600 yards (600 y is for .25 MOA)
The 700 yard MOA value is correct.




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I'll start off by saying that I have never used the app you are speaking of, but I have used other ballistic calculators to help guide me in 1000 yard shooting. Other calculators have usually landed me within 1 or 2 MOA at 600 yards and within 3 at 1000.

I looked over the numbers that you have entered into the app. Is it possible that some of the entered data is incorrect?

How did you get the value for the height of the scope? A small error in that value would have a pretty large effect on the calculated come-ups. For instance, 0.050" could affect the calculated come-ups by 5 or more MOA depending on the length of your barrel.

Next up, but probably much less impact, were you really shooting at sea level and 0% humidity at 78degF?

One more question, were you shooting with a tail wind when you measured all your drops?

Thanks Gman for the reply.
I don't think any of the primary values are incorrect. The only one that is entered, but not really needed is the "MOVE ANGLE" value of 90 degrees and I already changed it to 0 and it didn't change any of my values.

As for how I measured my scope height, I used the method the app recommended. I measured both the diameter of the scope and the barrel and divided by 2. Then measured the gap between the scope and barrel. I then added all three values together to get my final measurement. Looking back at their website, they say to measure the bell, but the "bell" is typically referred to the funneled shaped area that connects the main tube to the objective lens. So I might need to check back on that. Maybe fudge my numbers and see if it changes any.

As for temp, humidity, and elevation, I was not at sea level. Good catch. I did have the correct elevation of 1,033 at 78* and 25% humidity in there initially, but it wasn't much different. Probably a MOA.

oh and as for wind when doing my initial drop calculations. No sir, I had a 5-8 MPH crosswind that move my placement 6-10" to the right. (but I was only concerned with drop not windage at that time)

maybe compare against another calculator? run g7 ballistics? maybe calibrate scope?

When you start getting out to longer ranges, you have to take spin drift and the spin of the earth into account.

You need to use a G7 ballistic coefficient not a G1. The error in your drag model is compounding at distance

http://www.bergerbullets.com/a-better-ballistic-coefficient/

2nd post to add that if you use a ballistic program like 'Shooter' with a g7 bc, you can enter your drop data that you measured to calibrate the bullet velocity.

Agreed about the rotation of the earth. But I thought I read that wasn't a big issue until 1000+ yards. But still a factor

I'll see if I can see what the G7 bc is for my Hornady A-max.

I've been meaning to find another calculator and compare the two. Anyone have another option they like? Preferably free?? Just to use as a cross reference.

Also Pooh Ag....I actually emailed the Shooter App programmers about the velocity calibration feature and how I manually entered the true MOA reading and how it never adjusted the MOA reading. Here is what their response was:
"Velocity calibration only calculates and suggest a change to a single metric: your muzzle velocity.

The calibrator tries to find the closet average velocity based on your inputs. The calibrator is -not- altering your bullet path calculation. It's simply spitting out a new suggested muzzle velocity."

Dp

quote:

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Cool video making it easily understood

Great video. Thanks for sharing it

I changed my G7 BC to 0.240 and got a little closer on a few distances, but still off on most of them. Changing velocity helps some, but it only corrects the distances that I'm off and then makes the value that were originally correct, off.

I've had good luck with the Shooter App getting me close enough. (I've only shot out to 800 yards though). But it certainly illustrates why you have to develop your own dope chart. Another limitation you may not have considered is the constant g7 BC assumption throughout your bullet's flight. With the plastic tips on the A-Max and Accubond, I think this assumption really degrades as you stretch out there in distant. Hornady recently published some studies on this which led to their ELD line of bullets. Based on some back on the envelope calculations and my own experience with A-Maxes, I think their study is more than just advertising propaganda.

I entered your numbers into the app I use (Ballistics AE). For AB200gr, standard atmosphere, 3415 fps muzzle:

Range Drop (MOA)
100 0.0
200 -0.71
300 -2.13
400 -3.83
500 -5.73
600 -7.84
700 -10.14
800 -12.67
900 -15.43
1000 -18.47

The question I have is what atmospheric conditions your measured rounds were fired at?

What altitude are you shooting at?

I shot these loads at 1,033' elevation. Calm day at about 78* probably 20-30% humidity.

Level shooting range or do you have a downward look angle?

level to slighlty upward, but not by much.



Thanks again to all the input from you guys. I think I found out my problem. You can see it on this other forum where I posted the same questions.


http://www.scout.com/military/snipers-hide/forums/5542-ballistics/14820456-shooter-app-issue-incorrect-moa/ms/184537750


Main points on SniperHide post:

"Like I mentioned earlier, the info below the actual bullet drops are confirmed on the 200, 300 and 400y distances. Scope was set to 0 MOA and shot on a tall target. Then I made the mistake and "assumed" that the MOA per each 100 yards was just 1 for 1 (200y = 2 MOA, 300y = 3 MOA etc) which is not correct. I should have used the 0.01047 value. As for the 600 and 700 yard shots, I never measured the actual drop in inches with a tape measure. Shooter App got me close and then I tweaked my MOA until I got a good center mass hit. Then I just did quick math again and did 7 MOA (for 700 yards) X 20 MOA (what my scope was set to) = 140" "


"So, by updating my BC to G7 and making my altitude correct at 1033', my new 600 drop is now -95.8" and my 700 yard drop -144.9". MUCH closer to the values that Koby posted. So definitely more accurate. The 600y value is spot on with SHOOTER and the 700y value is 144.9 (so -1.68" off). PRETTY DAMN CLOSE!"

Pooh (and NJW and Arrow too)----
Now you got me curious, what's your rifle setup and distances you typically shoot?
Any advice, pointers or tips for a newbie?

https://texags.com/forums/34/topics/2760207

I have used the free IStrelok app with good success. I always end up hitting the target and then using the calibrate feature to adjust to what I actually had to dial.

I'm just getting started with long distance. I'm shooting 300 RUM as well, but ammo shortages have kept me from hitting the range as much as I'd like.

I bought Bryan Litz's DVDs to learn long distance shooting: http://appliedballisticsllc.com/.

Ya ammo prices on the ultra mag is stupid high at the store. Part of the reason I decided to start reloading!

I'm ready for fall to get here with cooler temps so I can get back out shooting. It's not enjoyable from May-sept

Want to reload some for me?

I wish I had the free time to help ya out with reloading. Unfortunately with an 18 month old, free time is really limited. Hell, it took me almost 2 years to get my 308 and 300 RUM dialed in where they are today!

I've got lots of load data though with Retumbo powder if you need a good starting point

Yes, I would appreciate you sending your load data. nwyman at viablecomputing com

I'm shooting a rem 700 sendero. What make are you shooting? I've been using the 180gr core lokt ammo which is pretty much gone off the market.

I'm shooting a custom .260 Rem with a Nightforce SHV 5-20 scope. I primarily shoot hand loaded 140 grain Hornady A-Max. This will change soon since Hornady discontinued the A-Max. My primary targets are at 500 yards and 800 yards (as far as I can shoot at home). I was shooting like crazy last year leading up to a Wyoming Pronghorn hunt. Unfortunately, I haven't shot much at all this year.

I'm a newbie too. The best advice I can give is: spend more time at the shooting bench and less time at the loading bench. I've got a bad habit of chasing the last 1/8 MOA at 100 yards, rather than taking a good load and shooting a lot at long range.