Drop/MV discrepancy

[907to406]

Not to get off track but also curious as to what ballistics AB's malfunction was. I was using it for years without issue until a few months ago and it was giving me DOPEs 4-8 MOA off from what it should of been. I've been using Shooter ever since...

As for the OP like everyone else said I'd triple check all your input into your ballistics calculator.

As stated above:
-Make sure your drag model is actually your G1 and not a G7 or a G7 and not a G1.
-Sight height measured from center of bore to center of optic.
-Make sure all your atmosphere inputs are correct to the current atmosphere/conditions you are shooting in.
-If you have a baseline zero then are entering in current conditions vs the calculator trying to use current conditions as a zero (not sure if your app has this or not).
-Make sure you are using the right bullet in your bullet calculator.
-Any chance a box of bullets could have been mislabeled or something? Have you weighed an individual bullet to verify?

I know all this is pretty repetitive and seems basic but I've definitely overlooked some stuff in the past that has had a big effect on POI down range. Let us know if anything else changes or if you get it corrected

 

[Jordan Smith]

A screen shot of your input variables in your ballistic app would help us diagnose.

 

[mt100gr.]

FWIW, I just crunched all the number for both my 300 and my 7RM on the Berger website calculator, Strelok Plus, Strelok Pro, and through AB and AB is 1.5+ moa more generous for both rifles at 1000 yards.

I know this isn't addressing helping the OP with his troubles but with identical inputs for all data, AB has the velocity of my 300 inflated by 200 fps at 1000.

The Berger calculator and both versions of Strelok are giving me corrections that are all within .16 moa of each other while AB is off by 1.5+ moa consistently.

 

[kbaerg]

While you have been given lots of advise and stuff to try I will offer my 2 cents. Start over from the beginning, and double check all your inputs. If you can I would recommend you use the G7 B.C. for the bullet which is 0.356 (from Litz book) as it will follow the drag curve better .

 

[LaHunter]

Are you shooting at a significant angle? If you are truly zeroed at 100 yards exactly, I'm not sure you can load enough powder in a 300 WM case to only be 28" low at 500 yards with a 215 grain bullet. That is a full 2 MOA error from where is should be impacting. How did you measure your distances when doing your 100 yard increment test with the same aiming point on the big sheet of plywood?

 

[mmw194287]

Are you shooting at a significant angle? If you are truly zeroed at 100 yards exactly, I'm not sure you can load enough powder in a 300 WM case to only be 28" low at 500 yards with a 215 grain bullet. That is a full 2 MOA error from where is should be impacting. How did you measure your distances when doing your 100 yard increment test with the same aiming point on the big sheet of plywood?

Yea, that's what I thought about the 28" drop....and I ranged from the target to the truck when placing the target and then ranged again before shooting from the truck.

I'm either bending the laws of physics or screwed something up at the most fundamental level. The second case seems most likely. I'm just going to start from scratch with re-zeroing, etc. Thanks for all the suggestions and advice everyone--it was useful to think about all the possibilities and a good reminder to assume nothing and re-check the basics.

 

[Ndbowhunter]

No way ur rifle is 28" drop.


The only assumption I've seen so far is that ur night force is spot on and your range finder is too.

Ass out of u and me.

 

[Ndbowhunter]

If you don't even want to **** with rezero and all that crap.

Pull a trigger way the **** out there. Watch the bullet splash, then correct off the windshield with your elevation turret. Your reticle is spot on. If you hit your original point of aim after dialing elevation then you can rule out turrets.

then go back to 50 yards. I'm guessing its around .4 inches high poa to poi.

If that's jacked then put some new batteries in ur range finder or range some goal posts at a football field.

 

[HellsCanyon]

Can you post of picture of your target board with yardstick or tape measure for reference?

Mike


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[mmw194287]

View attachment 51712



So as best I can figure, if my zero is actually high 1.5 MOA (essentially zeroed at 225), I'd be seeing the following drops from my 100yd POI: 2.5" @ 200, 6" @ 3", 16.5" @ 400, and 30.1" drop at 500. Pretty close to what it did, and seems like the most likely answer at this point given that it's the only way to make a calculated profile with the correct MV and BC fit my results. But in order to see what I'm seeing on the target in terms of POI relative to the bullseye, I'd have to be unknowingly holding low with pretty amazing consistency, right? Is that nuts or is there something that might cause that that I'm overlooking?

 

[HellsCanyon]

View attachment 51712View attachment 51716



So as best I can figure, if my zero is actually high 1.5 MOA (essentially zeroed at 225), I'd be seeing the following drops from my 100yd POI: 2.5" @ 200, 6" @ 3", 16.5" @ 400, and 30.1" drop at 500. Pretty close to what it did, and seems like the most likely answer at this point given that it's the only way to make a calculated profile with the correct MV and BC fit my results. But in order to see what I'm seeing on the target in terms of POI relative to the bullseye, I'd have to be unknowingly holding low with pretty amazing consistency, right? Is that nuts or is there something that might cause that that I'm overlooking?

Were you resetting parallax at each distance? What rangefinder are you using? Can you pace off the distance?

From what I'm reading, you didn't dial anything, didn't use your reticle, just held same POA (bullseye) for each distance?


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[mmw194287]

Were you resetting parallax at each distance? What rangefinder are you using? Can you pace off the distance?

From what I'm reading, you didn't dial anything, didn't use your reticle, just held same POA (bullseye) for each distance?


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Yep, adjusted parallax for each distance. I was using a Sig Kilo 2200, and I can't really pace off the distance. But essentially what I did was placed the target at 100 (ranged to the truck), double-checked from the truck to the target, and then when I moved it to 200 I ranged from the target out to a rock or something another 100 yards out, ranged back to the truck to check once I moved the target, and then double-checked ranging from the truck to the target before shooting.

And, correct, didn't dial, didn't hold over, didn't use the reticle--held same POA at each distance.

 

[HellsCanyon]

Yep, adjusted parallax for each distance. I was using a Sig Kilo 2200, and I can't really pace off the distance. But essentially what I did was placed the target at 100 (ranged to the truck), double-checked from the truck to the target, and then when I moved it to 200 I ranged from the target out to a rock or something another 100 yards out, ranged back to the truck to check once I moved the target, and then double-checked ranging from the truck to the target before shooting.

And, correct, didn't dial, didn't hold over, didn't use the reticle--held same POA at each distance.

Man that is really weird... What Chrono are you using?

Mike

 

[mmw194287]

Man that is really weird... What Chrono are you using?

Mike

Magnetospeed sporter.

 

[HellsCanyon]

Magnetospeed sporter.

Go back and confirm a zero at 100 yards, then go right to 500 and dial 5.75MOA and see where you hit. If you're back on the bullseye, I'd say you have a rangefinder off by about 50 yards.

Mike

 

[LaHunter]

Shouldn't he need to dial more like about 7.5 moa for a 500 yard shot, if he has a 100 yard zero with the 215 bergers and a mv of about 3000 fps?

 

[HellsCanyon]

Shouldn't he need to dial more like about 7.5 moa for a 500 yard shot, if he has a 100 yard zero with the 215 bergers and a mv of about 3000 fps?

You're correct that's what his drop SHOULD be, I was referring to his actual drop according to his first range session. 28.5"/5 (100 yard increments). Either way he needs to verify his 100 yard zero and the extended range is actually 500 yards, and see what his come up is.

Mike


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[LaHunter]

I gotcha. It just takes me a little longer to catch on.

 

[rayporter]

a GPS could verify the range finder.

 

[Jon Boy]

Is your range finder set to measure in meters instead of yards by chance?

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