Velocity Decay from Chronograph to Muzzle

[rockywlw]

Is there a simple way to calculate Velocity Decay from Chronograph to Muzzle? Is here software or what is the easiest way. I'm 10 feet from the muzzle with a 6.5 Creedmoor.

 

[LastShot300]

AFAIK, Coldbore and JBM have this featured, may be others tough.

 

[FatBoy]

measure it at 5' intervals out to 20-25'. We saw a 35fps change going from 15' down to 10'. I suspect muzzle to 10' is about the same. Or, use a magnetospeed...

 

[lash]

Is there a simple way to calculate Velocity Decay from Chronograph to Muzzle? Is here software or what is the easiest way. I'm 10 feet from the muzzle with a 6.5 Creedmoor.

I'm curious as to why you want to know this.

 

[Nik H]

Coldbore has a velocity retardation function. I don’t know how accurate it is nor the underlying method

 

[rockywlw]

I'm curious as to why you want to know this

I have never tried 1000 yard ranges but will this year. Wouldn't you want true muzzle velocity for the range data?

 

[FatBoy]

it won't matter. 10' chrono numbers are fine. Make sure you put your scope over bore number in right, and get close on the temp and altitude and plug them into JBM. You're gonna be within 1-2 MOA.

 

[lash]

Like Fatboy said. In addition, your ballistic app specifically asks you how far from the muzzle your chronograph is so that it can take that into account. There are plenty of things to think about when you first shoot at longer ranges. Don't make it more complicated than it has to be.

Now, if you are just a math nerd and want to know how to calculate it for fun, by all means have at it. But it is not necessary for your ballistic calcs.

 

[DocUSMCRetired]

Try this one: http://www.appliedballisticsllc.com/Articles/ABDOC121_VelocityDecay.pdf

Also we have an Android App that can calculate it: http://appliedballisticsllc.com/products/apps/applied-ballistics-toolbox/

Or if you do a proper MV Calibration you can just negate it.