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Load development ladder test

 
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  #8  
Old 10-24-2005, 10:27 AM
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Re: Load development ladder test

Cowboy,

In the ladder tests I have done, I always use multiple aiming points (sometimes on the same sheet of paper, sometimes different, depends on what I expect the accuracy of the gun to be) and make sure that the area where the bullets will impact has some markings or a grid in order to easily compare the targets. I'll often mark my targets A,B,C, and D. Shots 1-5 go into A, 6-10 into B and so on. The only time you have to look at two of the targets at once is when you are comparing shots 5 and 6, or 10 and 11, or... It has worked pretty well for me. If I was at home I would post pics of my last two from my 30-06 ladder tests using 168 BT's and 165 Interbonds. They used 4 aiming points each, and show nice distinct nodes at similar powder levels.


Carl Porter,

Interesting idea using the three shot group to improve the reliability of the test. My only comment is, I thought that the point of the test was so that you didn't have to shoot groups at all the different powder levels, that you could narrow down the range of powder levels to look for good groups at? By the way, my tests (all factory barrels) certainly don't string just vertically either, more scattered or elliptical.

Also, what is this optimal barrel timing method you speak of?
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  #9  
Old 10-24-2005, 03:31 PM
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Re: Load development ladder test

Ladder test with chrony does one very important thing and that is it allows you do find the middle of a node based on MV. You will need that, not only will the bullets cluster but the MV will also.

I always go for the middle of the MV node instead of the top end. you might be on the ragged edge and a rise in temp or humidity set you over on another day. Whereas if you go in the middle it stays in "tune" much better.

Finally, in order for you gun to show a cluster producing a cluster, ie it must be capable of at least .5 MOA, otherwise you do not know what is the cluster or what is just the aberation of the accuracy level of the rifle.

BH
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  #10  
Old 10-25-2005, 08:01 AM
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Join Date: Oct 2005
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Re: Load development ladder test

zingdingo,

You are right, the point of the ladder test is to reduce the number of rounds necessary. Unfortunately not all guns will throw a nice vertical string in a ladder test. These guns require more rounds per load to get anything from the test.

Optimal barrel timing is based on traveling shock waves in the barrel. In the cartoons when a gun is fired the barrel balloons out and the balloon travels down the barrel to the muzzle and spits out a bullet. In reality the balloon isn't that bad but it does travel down the barrel and back 3 or more times before the bullet leaves the muzzle. It's been shown that when the traveling wave reaches the muzzle the bore opens up slightly and this degrades accuracy. Best accuracy is when the bore is at it's minimum diameter. Optimal barrel timing takes this into account. So far in my experiments ladder testing has shown two or three nodes and the optimum barrel timing predicts them fairly close.



Optimal barrel timing
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  #11  
Old 10-25-2005, 09:30 AM
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Re: Load development ladder test

Ladder testing has been a tough one for me.
My max bench available range is 280. Last week, I shot a ladder with a T2K in 6xc. But was not able to see a best load.
32shts in .1gr increments. 105 bergers fully into lands. My 32shot group ended up being about 4", so even with a 32x NF scope, I wasn't able to follow and map each impact. There were 2 distinct velocity shelves with with an ES of about 2-4(I use an Oehler w/12ft screen spacing). Definitely not linear. So I threw together 10rnds centered in each low ES area, and really hoped I would be grouping well in one of them. But groups turned out poor there. This is where I dialed in the BOSS on my last rifle/load developement.

So I have to take pause and reapproach this.
#1 I have to setup somewhere shooting alot further.
#2 I need to explore different components to test.
#3 I need to find a wireless camera/monitor system.
#4 Next rifle gets a tuner
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  #12  
Old 10-25-2005, 09:58 AM
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Re: Load development ladder test

If they are all shooting that close, shot multiple targets with a reference point. That way, shoot say five to ten rounds at each target then you can overlay them and see your total grouping. If you wanted to get super fancy, photocopy the individual groups onto clear laminates so you can use a transparency and enlarge your target from a 4x6" target to 6-8'. Then you can see then nodes better maybe.

Just an idea!
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  #13  
Old 10-25-2005, 01:05 PM
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Re: Load development ladder test

couple points

1. shoot with .2 or maybe .3 increments
2. you really need 300 and better 400 yards.
3. movement will never be linear, often at angle left and right, but it will show clusters on both grouping and MV
4. walk/drive down,mark each shot and plot on sep piece of paper so you can track.
5. Record MV of each shot so you will see the cluster there too.

good luck

BH
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  #14  
Old 10-28-2005, 06:27 PM
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Posts: 294
Re: Load development ladder test

Thanks for the replies guys. Sorry it took so long to read them but I was hunting. I am going to leave it alone for the time being (its hunting season). I think I can do a little better and may try a different powder and a chrony. I will also go bigger increments and then step down when I get close. I think I will also start doing less shots at the same target to avoid the confusion of everything being in the same group.
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