Which BC do you true with? (TMK, ELDX and ELDMs)

[bojangles808]

There's g7 g1 and then the BC listed in AB quantum. except I thought litz is a berger guy so are those AB dopler BCs with Sierra and Hornady bullets really accurate? Wondering which one is a good starting point specifically on the 77 TMK and 108 eldm and 103 eldx when truing at 600.

@Formidilosus I thought i remember in one of your old posts saying g1 for Hornady bullets is fine but does that still ring true?

 

[Ajsomp]

I do G1. g7 is the newer model and probably better, but g1 gives me a reference for quick wind.

 

[Formidilosus]

There's g7 g1 and then the BC listed in AB quantum. except I thought litz is a berger guy so are those AB dopler BCs with Sierra and Hornady bullets really accurate? Wondering which one is a good starting point specifically on the 77 TMK and 108 eldm and 103 eldx when truing at 600.

@Formidilosus I thought i remember in one of your old posts saying g1 for Hornady bullets is fine but does that still ring true?

G1 versus G7 doesn’t matter. It’s engineers and dorks repeating what they’ve been told- a real G1 will give the same data as a real G7 BC until well beyond terminal range. Use Hornady’s g1 for their bullets- AB magically causes high impacts if you use their numbers for Hornady bullets. The g1 bc for the 77gr TMK is .420.

 

[HuntHarder]

Hasn't mattered for me. Usually use G7, but G1 drops are almost identical.

 

[Lawnboi]

Well known bullets…. There really shouldn’t be any truing needed at 600 yards.

Any of those will probably get you to .1mils in predictable conditions.

 

[Kjc103]

There's g7 g1 and then the BC listed in AB quantum. except I thought litz is a berger guy so are those AB dopler BCs with Sierra and Hornady bullets really accurate? Wondering which one is a good starting point specifically on the 77 TMK and 108 eldm and 103 eldx when truing at 600.

@Formidilosus I thought i remember in one of your old posts saying g1 for Hornady bullets is fine but does that still ring true?

The Doppler readings are found under “custom curve” in AB.

 

[Tahoe1305]

I’ve had good luck with G1s and most eldx. Out to 800yds or so maybe I need to tweak the velocity on the calculator 25-50fps to hit waterline. That’s how I was taught to true and it’s worked fine.

 

[Coleredding00]

I use G7. Never had many issues with it. Custom curves on both AB and 4DOF seemed to be further off for me.

 

[Jordan Smith]

Both can work well, as long as they are modelled correctly. The more closely the actual bullet matches the reference model (G1 or G7), the more the BC approaches a constant value. The G1 reference model is a flat-based spitzer, while the G7 model is closer to a VLD design. If you're using a G1 BC value for a VLD-type bullet, the BC value changes with MACH more than if you use a G7 model, but as long as that dependence is correctly captured, it will predict the same trajectory as the G7 model. Using a G7 model for slippery bullets just reduces the sensitivity of the model to variations. A custom drag curve essentially just precisely matches the BC to the actual bullet you're shooting with many MACH data points instead of only one or a few.

I generally use either the custom drag curve or the G7 BC value, depending on the bullet.