Ladder Test Minimum Distance??

[tomcatfan]

Can someone please explain why everyone says that 300 yards is the minimum distance needed to shoot a ladder test. I've seen many threads on ladder tests, but I don't want to hijack someone's thread to have this explained.

The way I understand ladder tests (which may not be correct) is that you use the same components and vary charge weights in a predetermined increments to isolate accuracy nodes in the barrel harmonics to potentially hone in on the “best” charge for your rifle given specific components. Where I get confused is at the claim, the more distance the better. That seems counter intuitive to me as at longer distances, environmental effects and shooter shortfalls are going to be exaggerated. Also at longer distances, poi differences will be amplified by variances in velocities. Won’t this potentially taint your results? The way I understand it, if your only object is to identify accuracy nodes, shouldn’t distance be minimized? Now I understand as distance decreases so does the distance between your shots. This could make interpretation a little harder. But by using calibers I can measure .001 inches.

I feel like I’m missing something here with ladder tests and by researching them, I think some other people are as well. What am I going to see at 300 yards that I won’t see at 100 yards?

 

[justinbaker]

Re: Ladder Test Minimum Distance??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Savage 10fp</div><div class="ubbcode-body">
Where I get confused is at the claim, the more distance the better. That seems counter intuitive to me as at longer distances, environmental effects and shooter shortfalls are going to be exaggerated. <span style="text-decoration: underline"><span style="font-weight: bold">Also at longer distances, poi differences will be amplified by variances in velocities.</span></span> Won’t this potentially taint your results? The way I understand it, if your only object is to identify accuracy nodes, shouldn’t distance be minimized? Now I understand as distance decreases so does the distance between your shots. This could make interpretation a little harder. But by using calibers I can measure .001 inches.

I feel like I’m missing something here with ladder tests and by researching them, I think some other people are as well. What am I going to see at 300 yards that I won’t see at 100 yards?
</div></div>



the underlined part is exactly what we want. With the varying velocities also come varying barrel harmonics.

As we increase the velocity we will find a couple nodes where the harmonics are similar, so we will see a couple shots with very little vertical dispersion.

But once we keep increasing the charge, the harmonics will change and the POI will change as well.


If we were to shoot this at 100 yards, it would likely be 1 big hole, so there is no way to find a Node.

As for environmental effects it doesnt matter. As we dont care about wind drift. All we want to see is the vertical spread.

Hope that makes sense

 

[tomcatfan]

Re: Ladder Test Minimum Distance??

Ok that makes sense. I guess the vertical dispersion was the key I was missing. So now the issue is, what do you do without a 300 yard range? The max range I have access to without driving 5 hours is 100 yds.

 

[justinbaker]

Re: Ladder Test Minimum Distance??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Savage 10fp</div><div class="ubbcode-body">Ok that makes sense. I guess the vertical dispersion was the key I was missing. So now the issue is, what do you do without a 300 yard range? The max range I have access to without driving 5 hours is 100 yds. </div></div>


with only a 100 yard range, get ready to start reading more

OCW or Optimal Charge Weight

http://www.optimalchargeweight.embarqspace.com/

 

[tomcatfan]

Re: Ladder Test Minimum Distance??

Thanks alot for the link. This kind of stuff is what makes this site so great.

 

[vinsonr]

Re: Ladder Test Minimum Distance??

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">
If we were to shoot this at 100 yards, it would likely be 1 big hole, so there is no way to find a Node.</div></div>

While it is very true that it will be much harder to find a node at 100, you will not get 1 big hole. Half grain increments in a 308 resulted in a 2.5" vertical spread over 2 grains of varget. I shot them expecting to see the climbing hole pattern and was surprised to realize they were dropping. It made sense after I thought about it for a minute. At any point at or before your zero the faster loads get there quicker than the bullet has a chance to rise, the faster ones having flatter shooting trajectories overall.

This stuff is fun.