Drop Chart Help

[cdixon1]

I had my first chance to shoot some long distance this year, but the drops I am getting from ABMobile (and my Fury 5000AB) start deviating from my actual drops past 600 yards (450 and 505 was first round impacts using AB data). I had an experience spotter who help walk me on target to get my actual come ups. Using those, I was able to make consistent hits at all ranges on a 12 inch plate.

Can anyone spot an issue with my input data? Anyway to explain why the 695, 860, and 1001 actual adjustments are so far off? Any thoughts on where to look/what to do next? It certainly could be me being a newb, but I just want to make sure nothing jumped out at the more experienced shooters. I am going to try to get back out and confirm again, just haven't had time yet.


7saum
2912 velocity (magnetospeed)
175 Berger Elite Hunter (.336 G7)
Scope Height 1.3
Zero 1" high at 100
Elv 2650
Station/Absolute Pressure 27.95 (from nearest airport)
Temp 60 degrees

Yardage	AB Drop (MOA)	Actual (MOA)
450	5.6	5.6
505	7.0	7.0
695	12.5	11.0
860	17.9	15.5
1001	23.1	21.5

I certainly appreciate any input, and thank you for your time.

Chris

 

[Dmagna]

Nothing is perfect. They get you in the ball park and then you can tweak things like BC to match up your drops. 1-2 moa off is pretty good at that distance.

 

[just_jon]

Scope height seems low to me. Most of mine are in the 1.6" to 1.8" range.

 

[Hydra6]

"Zero 1" high at 100". Assuming you have a scope with dialable elevation - why not zero at 100? Did you input the "1" high" zero into the ballistic solver?

Also, may need to "true" your data. Velocity at 600 yards and BC at 800+

 

[cdixon1]

Nothing is perfect. They get you in the ball park and then you can tweak things like BC to match up your drops. 1-2 moa off is pretty good at that distance.

That is good to know. Would you suggest tweaking BC/Velocity/Etc to match at a particular distance that I shot, then assume the inbetween yardages are correct? Unfortunately my range has set distances, so to shoot say 675 gets a little hard to do to confirm.

Scope height seems low to me. Most of mine are in the 1.6" to 1.8" range.

Thank you. I measure to the top of the barrel, not the center of the bore not thinking it through. I am 1.8" to the center of bore. I will update that and see what that does to the number

"Zero 1" high at 100". Assuming you have a scope with dialable elevation - why not zero at 100? Did you input the "1" high" zero into the ballistic solver?

Also, may need to "true" your data. Velocity at 600 yards and BC at 800+

Being this is a hunting rifle, I did 1" high out of habit mainly. The goal is to extend point blank range as far as possible, but I see your point. The 1" high was part of the data input in the solver.

When you say true your data, how exactly do you do that? Is that in the solver, or do you need to collect more data at those ranges?

 

[Hydra6]

I am not the expert; but, I get my data then confirm at distance. Say 600 yard target - goal is to hit a specific spot on target elevation. Say you shoot and you are 2 inches low at 600 assuming correct data and you held perfect, perfect trigger squeeze. Then adjust velocity in dope to get your data to match actual results at 600. Then shoot as far as possible - 800+ for example. Do same and see impact. Say impact low again - now adjust your BC in your data until the data matches results.

 

[Dmagna]

This is a good one to watch

 

[Dmagna]

 

[MOelkman]

Scope height seems low to me. Most of mine are in the 1.6" to 1.8" range.

Isn't scope height measured from centerline of bore to centerline of scope?

 

[ShtrRdy]

From what has been discussed thus far I would suggest two things.

1. Correct the scope height to be centerline of bore to centerline of scope. You might be able to measure from top of bolt to bottom of scope tube and then add 1/2 the scope diameter and add 1/2 the bolt diameter.

2. Either zero the weapon system at 100 yards or figure out what the zero distance is to give you 1" high at 100 yards.

 

[CaneBrake]

What's your zero atmospheric data vs atmospheric data look like when you make these shots? Double check that sight height, that seems abnormally low. Measure the centerline of the bore to the centerline of the scope. What's your MV variation? What scope? Tall target test? How much tracking error?

I can't replicate your drop data at all with the variables you gave. I can get either the longer distances to match or the shorter distances to match but not both. If your solver has an option for axial form factor you can tweak that as well to help the data match the real world. My opinion would be to ditch that 1" zero height at 100 zero and zero at a definable distance.

This is why I don't like relying ballistics solvers for longer distance. They can't always account for everything. They do have their place though,

 

[338 dude]

I had my first chance to shoot some long distance this year, but the drops I am getting from ABMobile (and my Fury 5000AB) start deviating from my actual drops past 600 yards (450 and 505 was first round impacts using AB data). I had an experience spotter who help walk me on target to get my actual come ups. Using those, I was able to make consistent hits at all ranges on a 12 inch plate.

Can anyone spot an issue with my input data? Anyway to explain why the 695, 860, and 1001 actual adjustments are so far off? Any thoughts on where to look/what to do next? It certainly could be me being a newb, but I just want to make sure nothing jumped out at the more experienced shooters. I am going to try to get back out and confirm again, just haven't had time yet.


7saum
2912 velocity (magnetospeed)
175 Berger Elite Hunter (.336 G7)
Scope Height 1.3
Zero 1" high at 100
Elv 2650
Station/Absolute Pressure 27.95 (from nearest airport)
Temp 60 degrees

Yardage	AB Drop (MOA)	Actual (MOA)
450	5.6	5.6
505	7.0	7.0
695	12.5	11.0
860	17.9	15.5
1001	23.1	21.5

I certainly appreciate any input, and thank you for your time.

Chris