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How do I calculate MV? No Chrono.

 
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  #1  
Old 08-26-2009, 08:17 PM
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How do I calculate MV? No Chrono.

Is calculating MV more like a best guess without a chronograph or can I get pretty close knowing barrel length, powder, bullet weight? What kind of formula/freeware do I use?
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Old 08-26-2009, 08:29 PM
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Re: How do I calculate MV? No Chrono.

Using the load info will not get you accurate enough for much, as different rifles behave much differently.

If you have a drop chart and all the environmental conditions, you can work backward and get a fair guess with one of the ballistic programs.

For example my 7mm Rem Mag, shooting 160gr Accubonds is sighted in at 200yds, the sight hieght is 1.5" and I have to crank 14.75 moa up to hit at 800yds when at 7480' elevation. By playing around with the program I can see that I am around 3000fps.

My chrono tells me That I average 3015.

Your best bet is to spend a couple hundred $$'s on a good chrono and use it. It will save it's cost in ammo over the next few years.

HTH,

AJ
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Old 08-26-2009, 09:02 PM
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Re: How do I calculate MV? No Chrono.

This may seem like a smartass answer buuuuuut:

If you have time lapse videography you could calculate the time it takes the bullet from the muzzle to some point downrange. I would expect this could cost a boat load, OR get a chrony for a lot cheaperů
OR,
Guess based on currently available data from ammunition mfrs - would be as good as not having a chrony.

Regards,
Lever
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Old 08-26-2009, 10:43 PM
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Join Date: Jul 2004
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Re: How do I calculate MV? No Chrono.

Quote:
Originally Posted by AJ Peacock View Post
Using the load info will not get you accurate enough for much, as different rifles behave much differently.

If you have a drop chart and all the environmental conditions, you can work backward and get a fair guess with one of the ballistic programs.

For example my 7mm Rem Mag, shooting 160gr Accubonds is sighted in at 200yds, the sight height is 1.5" and I have to crank 14.75 moa up to hit at 800yds when at 7480' elevation. By playing around with the program I can see that I am around 3000fps.

My chrono tells me That I average 3015.

Your best bet is to spend a couple hundred $$'s on a good chrono and use it. It will save it's cost in ammo over the next few years.

HTH,

AJ

+1

Before I could afford a chronograph I did about the same thing. I would shoot 5 rounds (Minimum) at each distance. 100,200,300,400,500,600,and on some rifles 1000 yards
using a target large enough to get all of the groups on it.(I used the brown rapping paper
on a 4" roll 4 to 6 ft tall.

Then I placed a contrasting aiming point placed at 12 o'clock high and aimed at it for each
group of shots at each distance.

When I was through I found the center point of each group at that distance and used the
drop to make my chart.

Then using the reloading manual from the bullet manufacturer I matched the drop to the
ballistic tables for that bullet weight and it got me close to the average velocity.

And after many years I finally broke down and bought a chronograph and boy was it easier.

And for working up loads much faster.

J E CUSTOM
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  #5  
Old 08-27-2009, 09:57 AM
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Re: How do I calculate MV? No Chrono.

"How do I calculate MV? No Chrono. "

You can't. That's why we buy chronographs if we really want to know.

I've seen book data off as much a 300 fps, both ways, for "max" book loads. I've also seen a midrange book load blow primers in a new rifle, meaning our books are only a guide and not a real good one at that; they simply can't be.

Last edited by boomtube; 08-27-2009 at 10:01 AM.
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