Thread: Need help making drop chart match up

300wsm Tikka t3
Feel like I have all the data but I can’t make the app match my real world findings
Hopefully some guru can sort it out in a minute and point me in the direction I’m going wrong
1.74” sight above bore
3195 fps MV (measured over a lot of shots with Garmin Xero)
1/11 twist Rate
Sighted at 100y
600y is bang on at 8.5 Moa
Sierra Gamechangers 165gr
.53 bc >2680 G1
.44bc <2680
.32<1300
Photo is off last group shot at 600y

What app are you using and how far off is it? What's your scope?

Tried a few Ab quantum and Ballistics AE Sig Saur tango 4, tracking seems fine with scope 0.25moa between 2-3 1/2 moa out when I play around with things such as velocity and bc

How are you measuring environmentals?

How does the 600 yard velocity line up with your muzzle velocity and chart?
GPM.

Having a play in AB -

The 600 Yd velocity lines up ok with your MV depending on environmental conditions.


No matter what I do you should need around 10-11 MOA of up.

Have you checked that you have a solid zero? Have you double-checked ranges? Incline? Scope adjustments?


Aero jump from a really strong R-L wind ?

You've measured your velocity with the most accurate tool possible.

The BC on AB is about as accurate as possible, and to generate that much error at 548M you'd be looking at a massive BC issue. Like 100 points of G1 only gives you 0.5MOA difference at that range. The AB BC isn't going to be off by 100 points. Maybe 10. You can't measure that by shooting on targets.


The issue really has to be in one of your inputs or the system - zero, range, environmentals, scope adjustments

Double check scope above bore line measurement, scope tracking accuracy.

Originally Posted by Tipzehh

Tried a few Ab quantum and Ballistics AE Sig Saur tango 4, tracking seems fine with scope 0.25moa between 2-3 1/2 moa out when I play around with things such as velocity and bc

I’ve tried a few different apps, and AB Quantum is pretty darn close for me if I get the inputs correct. 2-3.5 moa out makes me think there is something else going on.

Your sighted in at 200yrds and it works? Are you sure it’s 100yrds

tripple check your 100y zero, it is your baseline. ideally fire 2x 5 round zero groups.

you should be using a G7 BC, not G1 for a boattail bullet. even better use the AB custom curve if they have it for your bullet.

Never adjust your muzzle velocity as its been reliably measured, you can slightly adjust the AB provided BC but if you're changing it by more than 0.01 something is wrong.

ill try to dig out g7 values from bryan litz for the bullet later. should have it somewhere

Originally Posted by STC

ill try to dig out g7 values from bryan litz for the bullet later. should have it somewhere

Sorry. the version i have does not have them only tipped matchkings, which will not be particularly helpful:

The Litz AB G7 for the 165gr Gamechanger is 0.246

Is your range finder set in the right units? I need an extra 3.5 moa to get from 600 yards to 600 meters.