Thread: trajectory validation distance

So question for the wise folk on here, when validating drops how far do you need to shoot to get an accurate estimation of MV? Looking to validate a 7mm08.
Also is 2 points enough, eg 100yd zero check and measured drop at say 400yds? Or would you shoot 200 and 300 as well?
Im guessing like most things the more data points the better but would two work out accurately enough?

Cheers

100yd zero and measure drop at 400 should be good for a 7/08. Prob wouldn’t hurt to get 2 & 300 as well. Depends on how far you want to shoot.
All the other data needs to be good too though, temp, pressure, humidity

Validate it to the maximum distance you will shoot to. More steps/distances will give you a better picture of your ballistic curve


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For regular non-magnum cartridges I zero at 100m and drop test at 250m and somewhere between 300-400m. For the .308 it’s usually closer to 300m, for the 6.5mm it’s closer to 400m. I setup my .223 and .243 with drop tests at 250m and 325m.

It’s worth pointing out that if you are using an application like a Strelok, then it doesn’t matter if you don’t have a round number, as long as you have an accurate rangefinder, you can use whatever is easiest to shoot with a good backstop. It’s important to have the line of sight as flat as you can get it.

What I found is that if I want to extend my drop test range out to 500m then I need a really tall piece of plywood...

So far this method has worked well for me and I am shooting accurately past 700m with trajectory validated at half that range.

One thing that is really important to do is to test the tracking of your scope. You can have good drops data but a rubbish dial which screws everything.

I’ll add to what @MSL says which is quite often it isn’t really practical to validate at the distance at which you shoot, firstly finding an easy place to do that is quite hard and second as previously mentioned, the logistics of the target size. My 6.5 is mostly employed between 400-600m and a 600m target would need to be about 2.8m tall... But the logic is correct, if you are normally shooting at between 200-300m, then pick 100m, 200m and 300m.

When validating or truing you go to where your projectile goes into transonic and shoot to with in ten percent of that distance.
If you want to shoot past that you then get into the system of DSF (drop scale factor)
which then allows for predicting trajectories through transonic and then into subsonic .
In the kestrel 5700 elite it puts a small dot next to your remaining velocity when you go into transonic and a bigger dot when you get to subsonic..
It sounds a bit technical but quite simple once you've got a handle on it .
The 5700 also will give you a suggested distance to true at .
Todd and colby hodnett do some great tutorials on this that are worth watching.
If your serious about longrange get a kestrel 5700 elite, the one tool I never leave behind.

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Originally Posted by Hunty1

So question for the wise folk on here, when validating drops how far do you need to shoot to get an accurate estimation of MV? Looking to validate a 7mm08.
Also is 2 points enough, eg 100yd zero check and measured drop at say 400yds? Or would you shoot 200 and 300 as well?
Im guessing like most things the more data points the better but would two work out accurately enough?

Cheers

Here’s what I do if you don’t have a chrony.

Sight in middle of the bull at exactly 100 yards.

Open any number of available ballistic websites (try hornady.com they have a ballistic calculator). Put in the data you have eg BC of bullet, sight in distance, estimate of speed (say 2750 fps). This program will spit out your come ups out to whatever distance you choose.

Go to 400 yards, adjust your scope and fire 3 shots. If they are 2 inches below the bull you need to come up 2 clicks. 1 click is roughly 1 inch at 400 yards (Moa). If 3 inches high you need to come down 3 clicks.

At this point go back to the ballistics program and back off the speed/or increase it till it fits where the bullets have landed.

Go back to 400 and have another 3 shots. Hopefully you are ready to go.

Chart can now be set up from 0-400 yards.

cheers guys, pretty much what I thought.

Hopefully can find somewhere on mates farm suitable to get some distance.

This is the calibration / truing page in applied ballistics.
Simple but effective.
You can just use the first range or less
You just put in what you actually had to dial for that distance and it will change your velocity to real world speed when it asks if you want to use this data.


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Originally Posted by andyanimal31

This is the calibration / truing page in applied ballistics.
Simple but effective.
You can just use the first range or less
You just put in what you actually had to dial for that distance and it will change your velocity to real world speed when it asks if you want to use this data.
Attachment 138852

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That is for my 6.5x55 using 143 eldx at 2720

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To truly verify your MV you need to shoot to a range that is 10 percent less then the point where your projectile goes transonic. If you wish to shoot further where your projectile is subsonic then that is a seperate verification that you need to do aswell. For most hunting applications simply choose a distance beyond what you would shoot game at and verify to there. For a hunting rifle I would normally try do something like 300, 500 and 700 making sure I know my atmospheric conditions and the zero is true.

Originally Posted by stagstalker

To truly verify your MV you need to shoot to a range that is 10 percent less then the point where your projectile goes transonic. If you wish to shoot further where your projectile is subsonic then that is a seperate verification that you need to do aswell. For most hunting applications simply choose a distance beyond what you would shoot game at and verify to there. For a hunting rifle I would normally try do something like 300, 500 and 700 making sure I know my atmospheric conditions and the zero is true.

You need a perfect zero then just shoot and validate past the distance you will never shoot .
Once you have done it you dont have to do any validating back from that as your app has all the info you need to give you the right solution.
You will be just wasting ammo unless you just want to play and theres nothing wrong wit that either

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Originally Posted by andyanimal31

You need a perfect zero then just shoot and validate past the distance you will never shoot .
Once you have done it you dont have to do any validating back from that as your app has all the info you need to give you the right solution.
You will be just wasting ammo unless you just want to play and theres nothing wrong wit that either

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Yup correct. I normally just do some shorter ones for a warm up to make sure I am shooting right. Oh and also because it’s fun! haha.

Often your long range is up in the hills somewhere. Remember the altitude affects air pressure a lot. At 1000m above sealevel Its about 80% which is equivalent to increasing your ballistic coefficient by 25%. So use a barometer eg in your phone or if youve got one on a kestrel. And check on the day at metservice and the adjustment for the ICAO standard atmosphere (wiki or gooogle). Work out how to allow for thT onyour ballistic app.

Start with the bc from brian litz Bullet database.

Dont adjust your mv too much to match your obsserved trajectory. Use an actual tall target and measure drop with a tape measuree because clicks can be out. Myguess is clicks are no more accurate than a chrony. ?

I did 100m 300m and 500m when I started with my 7mm08. But had a lot of trouble hitting a target at 600m until i had a shot on an 800 yd range and got the final tweakings right.

It wont hurt to use 800m if you can get it because you may want to shoot at targets further than you shoot at deer.

Around 900 m my 7mm08 goes subsonic and the bullets go into a parallel universe.

Ask on here and people will point you to litz, ICAO and so on if you need.

Thanks for going to the trouble of putting that together, really helpful!