Range Report First time over a 1000 . . . not what I expected

[glock24]

After more than a year of building, testing, and practicing, I finally received my opportunity to shoot some four digit distances this weekend. The rifle was a rebuilt Sako TRG-S in 7mm Remington Magnum behind a 162 grain A-Max at what turned out to be 2950 fps (more on that later!)

I've had plenty of practice out to 500 meters, and was getting quite proficient at killing 3" clay pigeons. My DOPE seemed solid and was confirmed at 100m, 300m, and 500m. I used JBM's trajectory values with Litz's BC. I even checked my zero the day before attempting this longer distance.

I was given permission to use a local farmer's property. My 15"x25" steel IPSC target was placed in an open field, and my range finder pinged it at 1054 meters. The full value left to right cross-wind was steady off Lake Michigan at my guesstimated 13-18 mph.

According to the math, I needed 8.7 mils of elevation with a 2.6 mil hold for the wind. WELL . . . 37 goddamn shots later I finally hit the target!

In hindsight, I made a couple rookie mistakes. Obviously assuming my DOPE was good at untested distances was foolish, but I could have also helped myself greatly by placing my target against some sort of hill or backstop as to allow me to see my misses.

After the frustrating trial-and-error method of a little high, a little low, a little left and a little right was completed, my successful DOPE was 9.2 mils of elevation and 3.0 mils of windage (the wind turned out to be closer to 20 mph)

I was actually pretty damn close the first time, but since I was shooting blind, it took quite a bit of ammo to find my target. Stupid!

Interestingly, when I went back to JBM's trajectory calculator and starting playing with velocity, I was able to dial in a flight path that passed through all my tested points; 100m, 300m, 500m, and now 1050m. This new flight path had a velocity of 2950 fps. Before this, I was using 3000 fps, and it also passed through 100m, 300m, and 500m, but unfortunately put me 0.5 mils low at 1050m. Putting all my trust in my $100 chronograph was also a mistake. Live and learn I suppose!

I can't wait to try it again. This time I'm hopefully a little smarter. A word to the wise . . .

Also, anyone with more field experience, please critique my logic and let me know where I could of done things better.

<span style="font-weight: bold">The rifle</span>

<span style="font-weight: bold">Digital pic (1x) of the field</span>

<span style="font-weight: bold">Digital pic (4x) of the field</span>
You can just barely make out a white spec in front of the treeline, where the plowed field turns to taller grass

<span style="font-weight: bold">The results </span>
As you can see, the hits are low @ 9.2 mils. I decided to call it 9.3 mils in my logbook.

 

[lanwickum]

Re: First time over a 1000 . . . not what I expected

Very nice, and lots of fun isn't it?

Were you able to read station pressure or denisty altitude when you were shooting? At 1000yards this does become important.

Keep learning and be safe....

 

[glock24]

Re: First time over a 1000 . . . not what I expected

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: montana</div><div class="ubbcode-body">Very nice, and lots of fun isn't it?

Were you able to read station pressure or denisty altitude when you were shooting? At 1000yards this does become important.

Keep learning and be safe.... </div></div>

Thanks. And yes, loads of fun!

I took altitude reading from my GPS (800 ft). All my DOPE confirmations were done at 900 ft, so I figured I was okay.

Question though; assuming the altitude shift was large, what would be my strategy? Do I simply apply an offset, or am I stuck reconfirming my drops?

 

[lanwickum]

Re: First time over a 1000 . . . not what I expected

Not altitde, but density altitude. Similar to station pressure. This is the atmospheric pressure for were you are at when you are shooting. I live at 3400ft and have seen station pressure of over 7000ft when shooting. So, I have to adjust as if I am shooting at 7000ft or what ever station pressure is when I am shooting. Not a huge thing at 500, at 1000 you notice it. You could have had 3000fps muzzle velocity and other factors could have changed your POI that you didn't notice.
I'll try to run some numbers using your data to show what your station pressure could have been to get your results.

Note that this isn't the only thing to throw you off, but one of the more common things. Always remeber KISS when shooting longrange. Keep It Simple Stupid. I don't what you to start reading into everything and blaming tidal forces on POI errors.

 

[glock24]

Re: First time over a 1000 . . . not what I expected

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: montana</div><div class="ubbcode-body">Not altitde, but density altitude. Similar to station pressure. This is the atmospheric pressure for were you are at when you are shooting. I live at 3400ft and have seen station pressure of over 7000ft when shooting. So, I have to adjust as if I am shooting at 7000ft or what ever station pressure is when I am shooting. Not a huge thing at 500, at 1000 you notice it. You could have had 3000fps muzzle velocity and other factors could have changed your POI that you didn't notice.
I'll try to run some numbers using your data to show what your station pressure could have been to get your results.

Note that this isn't the only thing to throw you off, but one of the more common things. Always remeber KISS when shooting longrange. Keep It Simple Stupid. I don't what you to start reading into everything and blaming tidal forces on POI errors. </div></div>

Density altitude is a new concept for me. Thanks for the lead on a new research topic.

Is this variable something I can plug into JBM's calculations? Any opinions on where I should start learning about this?

Thanks again

 

[lanwickum]

Re: First time over a 1000 . . . not what I expected

You simply punch it in as if it is the altitude you are at. A lot of simple weather machines give you this info. Kestrel is one example.

 

[glock24]

Re: First time over a 1000 . . . not what I expected

Yes. Thank you

I've been doing some reading;

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1073450&page=1

 

[lanwickum]

Re: First time over a 1000 . . . not what I expected

For 3000fps with 162 a-max at 800ft elevation I get 8.8mils. and 3.9mil windage for 20mph full value. This is for 1054meters.
With the above info I calculate you would need about 2920fps to get 9.3mils.

In order to get the 9.3 mils you would need a very high pressure area at 3000fps. your pics don't look like it to me with all those clouds. Although a .5 mil change from predicted is not out of the ordinary in my experience.
You are best off trying it again. Keep good notes.

 

[glock24]

Re: First time over a 1000 . . . not what I expected

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: montana</div><div class="ubbcode-body">

In order to get the 9.3 mils you would need a very high pressure area at 3000fps. your pics don't look like it to me with all those clouds. Although a .5 mil change from predicted is not out of the ordinary in my experience.
You are best off trying it again. Keep good notes. </div></div>

So keeping with your KISS principle, you'd agree my DOPE wasn't the best in the first place?

I will investigate this concept of density altitude from now on, but I agree that I need to keep concentrating on the fundamentals also.

What is your preferred method of calculating density altitude? Do you use a weather station and a PDA, or refer to a data book?

Thanks again.

 

[Criver600]

Re: First time over a 1000 . . . not what I expect

You did fine.......... its harder than it looks. A 1.5 moa wide by 2.5 moa tall target is pretty damn tough without a spotter. We get a bunch of new shooters at our Monday evening 1000 yard practice at Oak Ridge Sportsman Association. Depending on their ammunition we eventually get most of them on paper. Contrary to popular belief a short barreled rifle and factory ammunition is a rough way to get into Long Range shooting KD or otherwise.

 

[665.0coupe]

Re: First time over a 1000 . . . not what I expected

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: glock24</div><div class="ubbcode-body">What is your preferred method of calculating density altitude? Do you use a weather station and a PDA, or refer to a data book?

Thanks again. </div></div>

I did a quick google search and it looks like the Kestrel wind meters in the $250 and up price range calculate density altitude.

 

[steelcomp]

Re: First time over a 1000 . . . not what I expected

Good write up!

 

[Short-bus]

Re: First time over a 1000 . . . not what I expected

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 665.0coupe</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: glock24</div><div class="ubbcode-body">What is your preferred method of calculating density altitude? Do you use a weather station and a PDA, or refer to a data book?

Thanks again. </div></div>

I did a quick google search and it looks like the Kestrel wind meters in the $250 and up price range calculate density altitude. </div></div>

This is the Kestrel 4000 that I bought and where I bought it from. It does DA. I'm glad I bought the higher end model, I was just going to get the 3500.

http://www.ambientweather.com/ke40powestod.html

$209 with a free pelican case or another case, it's a good deal.

As for the shooting, don't be discouraged. I have yet to find a place where I can get that kind of distance around here. I'm working on it though. I would like to get my dope for my rifle out to 1400yards. I used my exbal to do my calculations the last time I was out, however I found it to be almost 3/4moa off (too much adjustment) at 700 yards, it's still a hit, however I prefer for my equipment to work exactly as requested.

Branden

 

[lanwickum]

Re: First time over a 1000 . . . not what I expected

I use a Kestrel. Not cheap for a lot people starting out. Lindy's article in the above thread you posted is an excellent read about density altitude. That will tell you way more than I could.
As per why you were low by .5moa. Could be a number of things, could be one big thing. I don't know.

KISS simple means just that keep it simple stupid. Stupid as in we can not put in all the varibles when it comes to mother nature, know we are stupid. Simple means to not make excuses and reasons for a miss. Again, know we are stupid. As you practice what once was hard will be easier, that is why we practice.

+1 what criver said
you were shooting .65 miles.

 

[glock24]

Re: First time over a 1000 . . . not what I expected

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: montana</div><div class="ubbcode-body">As you practice what once was hard will be easier, that is why we practice.

+1 what criver said
you were shooting .65 miles. </div></div>

Amen to that.

Thanks again!

 

[MontanaMarine]

Re: First time over a 1000 . . . not what I expected

It's tough in that kind of wind. With a 15" wide target, you only get 7.5" error before missing. Your 3.0 mil holdoff is about 113" at that range, in constantly changing wind...

 

[mdesign]

Re: First time over a 1000 . . . not what I expected

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MontanaMarine</div><div class="ubbcode-body">It's tough in that kind of wind. With a 15" wide target, you only get 7.5" error before missing. Your 3.0 mil holdoff is about 113" at that range, in constantly changing wind... </div></div>

Was thinking the same thing. I would say you did pretty well actually on a small target. You have a great setup there to practice at long range and before you know it you will be quite good at it. Good, honest write-up.

 

[xringdb]

Re: First time over a 1000 . . . not what I expected

Your chronograph may be accurate and your JBM dope may have been dead on. A left to right crosswind will move your POI down in a right hand twist barrel, while a right to left crosswind will move your POI up. This, of course, is more pronounced as range increases. This has been called Bernoulli's effect, magnus, coning, repose, yaw and other names over time.

It is hard to predict the value on a cold bore shot as the wind can have different amounts of influence at the muzzle, at the target and of course in between the two. It would be a trigonometric equation of the highest order.

I don't know how well I explained this, but I have tested it enough at distance to convince myself it does exist.

food for thought

 

[flims]

Re: First time over a 1000 . . . not what I expected

Do you know the extreme spread of your load?

it must be pretty low, the vertical spread of those 5 shots at the lower part of the target seems to be about 5" albeit stringing horizontally due to the wind.

 

[glock24]

Re: First time over a 1000 . . . not what I expected

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: flims</div><div class="ubbcode-body">Do you know the extreme spread of your load?

it must be pretty low, the vertical spread of those 5 shots at the lower part of the target seems to be about 5" albeit stringing horizontally due to the wind.

</div></div>

No, I'm sorry, I don't have my chronograph numbers handy. I do need to keep better records!

 

[laylowlong]

Re: First time over a 1000 . . . not what I expect

Must have spotter or backstop to ease the process of walking in your shots. My game is 3 shots to zero. You have to know your equipment. Score yourself a piece of sheet metal as a backup behind your plate... dust it with a bit of paint and you will be able to spot your misses... a dirt berm is best but doesn't look feasible where your at. Out here in my area, it's nothing but dirt, dirt, and hills of dirt.... kind of make it easy. Good going in any case.

 

[stenger]

Re: First time over a 1000 . . . not what I expect

Now i think i am confused!! i have a kestrel that tells you the alt., temp, and pressure. I then put all the numbers onto my exbal program, i put the pressure that the kestrel gives me in the pressure at alt. space, not in the pressure at sea level space and then hit caculate. Am i doing it right??

 

[Lindy]

Re: First time over a 1000 . . . not what I expect

I cannot tell from what you've written what you're doing.

Read this article:

http://www.arcanamavens.com/LBSFiles/Shooting/Downloads/Baro/

Now, when using Exbal you need to do two things.

One is make sure that the altitude reference in the barometric pressure window of the Kestrel is set to zero, so the Kestrel is displaying the station pressure.

The other is to make sure the "Calculate Std. Pressure" box in Exbal is <span style="font-weight: bold">not</span> checked. Then enter the station pressure in the pressure window.

 

[Graham]

Re: First time over a 1000 . . . not what I expect

Lindy's method above is what I use, and it works well for me for cold bores at 1000.

At RO a few of us set our Kestrel to zero and did not use the altitude input on Exbal while others tried deriving and entering the altitude. Lindy's method was simpler, more accurate, and better: primarily because, with fewer variables to consider, there was less opportunity for error.

The wind is the always the problem you can't get rid of.

Glock24, talk to your brother-in-law, do some shopping, and come out with us to Young's next weekend:

Kestrel $250
Exbal $ 75
A cheap Palm to run it on $ 99
Cold bores on 1 MOA targets at 1000 - Priceless!

 

[JRose]

Re: First time over a 1000 . . . not what I expect

Guess what, you actually went out and SHOT! Hit or miss, I bet you learned, or are about to learn something huge. I bet next times a bit better for you.


A bad day shooting us better than a good day......