Can you reverse engineer velocity somehow?

[cdn shooter]

So why not buy a Chromo?
While watching an individual use a chrono with one set of screens at 3 feet and getting a second reading through 5 feet. Since there was a difference on 12 fps on the two readings, he determined a loss of 6 fps. Therefore, at 300 feet, according to his calculations the bullet would lose 1800 feet per second in 100 yards.
now if the bullet started out at 3000 fps it would be coming back before it got to 200 yards . . . Yeah right . . . and chickens have teeth!
The BS that some people will spread!

Sounds like you grasp this already but....All a person needs is CHRONOGRAPHED! data at 15-20ft then get a real bc for your bullet. It can be a manufactures data, book (aka litz) data then confirmed drop data that you achieved on your own. The point is, without the starting chrono data you are guessing. The reason is, bc values are only estimates until proven by real world drop based on a starting velocity. This reverse velocity thing is so wrong that anything thought to be learned by it is so screwed up, a person woudn't know what data to analyze when things go wrong.

 

[AOWM]

Nonsense. With good BC data on the bullet and accurate drop measurements over several different ranges (especially out to 600yds, as OP states) it is quite possible to use a ballistics calculator to figure out the muzzle velocity within 50fps at least, probably better.

Now, why OP wants muzzle velocity as opposed to simply measuring the come ups on his 600yd range is a different question. Myself, I would rather have the actual measured drop data than the velocity.


Mark

Yes, accurate measurement of sight height & ballistic coeficient and bullet drop at three different ranges can be used to get a very accurate measure of velocity...
of course to get an accurate measure of bullet drop without firing alot of rounds you will need an accurate firearm.
And yes it is so much easier to just use the chronograph.

 

[jethunter]

I lack a chrony. So, I'm wondering if I can zero at 100 yards then shoot at 600 or so, and based on the drop of my projectile, determine velocity (roughly)?

Has anyone done this?

Yes you can do this.

Zero at 100. Shoot target at 200 yards and 300 yards and measure the drop from zero. Punch the numbers into any of the online ballistic calculators - JBM is a good one. Keep adjusting the entered velocity until it matches your measured drop at both distances.

You'll need to know the BC of your bullet, and you should take the average drop from a minimum of three x 3 shot groups at both distances.

Your results will be within 3-5% usually. The variables that are hard to nail down are BC - manufacturer's published data is not always accurate.

If you are a good consistant shooter with good range conditions you can get reasonably accurate numbers.

 

[Tex Critter]

If you want a ball park figure (roughly) for velocity consult a reloading manual.

 

[deadeyes40]

the load data that came with my lee die set.has it listed that by taking the max velocity for a load divide by the max powder charge for the same load multiply by the exact powder charge in your load will give you an approx. muzzle velocity.not sure how accurate it is.

 

[kawiguy]

Go to vortex optics website. Use the long range ballistics calculator. It is the G7 calculator. Put in your estimated values. Go and shoot. Punch the actual drop data in and it will calculate a new adjusted muzzle velocity and a new drop chart. They have a video and everything.