Validation question

[g0cherr]

I have been on this site for a few years, and the knowledge I have acquired has been a great help in getting me pointed in the right direction, learning long range shooting. I have a dilemma I can't figure out, and it is probably something I'm just overlooking so I need help. I am shooting a browning A bolt Stainless stalker in 300 WSM with a SHV Nightforce 5-20x56. I have ran it through the ladder test and it is tracking perfectly vertical, zero to 40 MOA. My load is a hand load with a consistent 5/8 group. I am shooting a Speer 180 BTSP, with Winchester cases, CCI large rifle magnum primers, and 64.5 grains of IMR 4350. Across the chrono I am getting an average of 2927 fps. 2 trips to the range for validation and i get the same results on both trips. I am using the Applied Ballistics app and have studied in detail the manual to make sure all inputs are correct (as I believe it). Here is where it gets interesting and I can't reconcile the data. I have a 200 yard zero, at 700 yards it calls for 13.75 MOA but actual shooting took 16.25 MOA scope adjustmet to zero. I entered that into the program for validation and it changes my MV to 2699. I know chronos aren't always accurate but this isn't close. So while set up, I had a great rock hillside to pick closer targets. I picked a good flat rock at 465 the new validation called for 7.5 MOA but actual shooting took 9 MOA to zero. From what i have read, BC doesn't come into play until you get out to 1000+ yards so I don't know how to reconcile these validations. No matter what I do with the MV I can't get the program to match these 2 validations, I even messed with BC, but it changed a little but not anywhere close to enough. I need help understanding what I am missing. Thanks in advance for your advice.

 

[dok7mm]

What brand chrono are you using? That could be part of the difference, but I'm leaning toward a wrong input in your program. That's usually what it turns out to be.

 

[g0cherr]

The chrono is a Competition Electronics ProChrono Digital.

 

[dok7mm]

I just ran some generic dope on shooter and it's not far off of your dope.

 

[dok7mm]

If your zero offset is correctly entered and you're sure inputs are otherwise correct, it sounds like the chrono numbers are off a good bit. Shoot your drops and adjust the speed to match them. If they are consistent, go with that.

 

[g0cherr]

There in lies the problem. If I go with the 700 yard validation it throws the 465 moa off and if I go with the 465 yard validation it throws the 700 yard off. How can that be?

Sounds like I need to double check all my inputs again.

 

[BallisticsGuy]

One of your inputs is definitely hosed. DM me and I can help you figure out which one. This is sort of my thing.

 

[Hatrick]

Could it be an elevation problem? Sealevel and up.

 

[g0cherr]

i zeroed at 5100 feet and shot my validation at 4800 feet. All of those environmentals were entered in AB.

 

[FlGunner]

I ran into a similar situation when I first got me Kestrel 5700. Not sure if you have access to one but I initially set my data and used True MOA and was hitting low and my validation to get on target killed my velocity and I was again off at other yardages. I switched to shooter MOA and was dead on. Sometimes I believe it's a matter of what output you get if you don't know what the difference is. Or at least that was the case for me. I was also always low using the AB app on my phone.

 

[g0cherr]

Thank you for you reply. I am going to show my ignorance here and ask what True MOA and shooter MOA are?

 

[FlGunner]

A true minute of angle is 1.047" @ 100 yds.... Shooter moa is basically an inch at 100 yds. I've recently bought a Kestrel 5700 and while I initially set it for TMOA, I hit low at almost every yardage. The further I shot, the lower I hit. I double, triple checked inputs. Then calibrated muzzle velocity and to hit at say x yardage it'd drop my velocity from 2950 to say like 2830. Then I'd be off at a different yardage. So I switched it over to SMOA and reset my muzzle velocity to 2950 add I've been dead on ever since. I think it's got to do with the click value of your scope as to which one you use. It didn't come with any instructions or manual for whatever reason. My Vortex PST says1/4 MOA on the turret but evidently is more closer to a 1/4". This is just been my experience and some of the more experienced guys can correct me if I'm misspeaking here.

 

[BallisticsGuy]

That would put him off by about 4% which would be about half a minute or so at 700 if I'm doing my pre-coffee math right. I've done a workup on the ballistics for him and it honestly looks like his MV would have to be around 2700fps for it all to work out. No change to BC, BP, zero, etc... or combination of changes pulls the numbers in to shape except for that. When set up for 2680 at his elevation and with everything else set up the app I make shows within 3/4MOA of his actuals so far which is more or less his group size plus some minimal shooter/ammo slop.

 

[J E Custom]

It sounds to me like you have the wrong Bullet BC. Bullets have different BCs at different velocities that have to be accounted for.

Try a lower BC in your program and you will see the difference. If you adjust the bullet BCs to match the actual drop It will closely match your actual drop at all distances and give you an idea of actual velocities.

J E CUSTOM