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Chonograph speed vs scope dial up at 600yards

B_Thomas

My go to load on the 6 BRX is 2985 fps avg. (Magna Speed Chonograph)

Shot this load last weekend at 600 yards.. Calculated come-up was 11.5 MOA for the 105g Hybrid (Litz corrected) I had to dial 12.4 MOA? Backing in the ballistic calc values show only 2900 fps?

Using Shooter app on my phone.....
 
darn...app and real life did not match..who would have guessed!
do you know for a fact that every input was correct ?
did you adjust velocity to match the app ?( at the muzzle, at 10 ft ,where ??)
altitude, temp pressure...a real simple one scope centerline above the bore ?
lots a variables and the app is a tool not a bible!
 
B_Thomas said:
My go to load on the 6 BRX is 2985 fps avg. (Magna Speed Chonograph)

Shot this load last weekend at 600 yards.. Calculated come-up was 11.5 MOA for the 105g Hybrid (Litz corrected) I had to dial 12.4 MOA? Backing in the ballistic calc values show only 2900 fps?

Using Shooter app on my phone.....
Click to expand...

What BC used? Does your app have a scope height entry?
I've used a few and found AB to be the most accurate.
 
hogpatrol said:
What BC used? Does your app have a scope height entry?
I've used a few and found AB to be the most accurate.
Click to expand...

Bullet library in the APP list it at .536 G1

scope height, I had set a 1.5".

Went to Bergers Ballistic calculator, It shows 11.34 MOA up. Something does not added up.............
 
Can we get all of your inputs? barrel twist. exact measurement of scope CL to bore CL to two decimal places, name brand of scope and inches or moa clicks, twist rate, average MV over ten shots. I did a rough workup with what is supplied so far and came up with 11.4 for 600 yards. One or more inputs are probably incorrect.
 
Do you have your zero data saved and then input real time conditions for your shooting session. We use AB and if data input is correct it’s very close on elevation. Good luck
 
hogpatrol said:
Can we get all of your inputs? barrel twist. exact measurement of scope CL to bore CL to two decimal places, name brand of scope and inches or moa clicks, twist rate, average MV over ten shots. I did a rough workup with what is supplied so far and came up with 11.4 for 600 yards. One or more inputs are probably incorrect.
Click to expand...

Yup, I've gone over all the variables again and get 11.4 MOA also.

I need to run the remaining loaded rounds from that match and verify the chonograph numbers again. It was around 70 degrees when I ran the load against the chon and 45-55 degrees during the match. That should not make 85 fps drop would it?
 
Are you sure the barometric pressure and temperature were correct? If so then adjust the muzzle velocity to get the actual dope, it may take a few outings at several environmental conditions to fine tune.
 
I would start with environmental. This is the first place most people get bad results from. Shooter App works, but you need to give it good info. I have used G1 and G7 with 105 hybrid and gotten the same output. Also don't use the adjusted MV, that will just burn you later at different distances. Find out what has not been inputted correctly.
 
You need a kestrel with a ballistic app. A phone app will never be as accurate. The kestrel will have all info readily available.
 
gilmillan1 said:
You need a kestrel with a ballistic app. A phone app will never be as accurate. The kestrel will have all info readily available.
Click to expand...

AB with a smart phone pulls in weather data from the nearest station. Unless out west or some other place where you are far away from the nearest reporting station (an airport with weather gathering instruments) and conditions are changing rapidly, the only thing the Kestrel adds is wind where you are standing.

Edit, I've used the Kestrel.
 
As others have said,

Make sure scope height is correct (s ounds like you did not measure it but went with default.

Make sure you are zeroed. AB has a function to correct for an adjustment that foes not zero exactly.

Tall target test. are your turrets moving the indicated amount.

All three, if off a little will add on you quick.
 
Scope height will really throw you off if wrong. But, the thing that has bitten me more than anything over the years, is not having a perfect zero to start with. Good luck and keep us posted.:);)

Paul
 
gilmillan1 said:
You need a kestrel with a ballistic app. A phone app will never be as accurate. The kestrel will have all info readily available.
Click to expand...
This is not a solution. I have seen more guys twirling kestrels at matches like "tactical fidget spinners" and still missing targets. Shooter, JBM, AE, Strelok, Etc, will all give you good data if you if you use them properly.

Also the sight height is not going to effect as much difference as you posted. A bad zero however will screw you up. My money is still on environmental or bad input.
 
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