Ladder Test - Analysis

[rymart]

I attempted my first ladder test this afternoon at 400 yards. It not sure that it went very well... The rifle was a 6mmAR T40 with 105 gr Amax's and Varget. Starting load was 29.1 gr, increasing to 30.9 gr in 0.3 gr increments. Conditions were as follow; When I got to the range, it was calm. By the time I set up my target and lined up the chronograph, a thunderstorn could be seen in the distance and the wind had picked up slightly (blowing from left to right from 7:00 to 8:00). By shots #2 and #3, the wind had picked up to a gusty 7 - 12 mph. By shot #5 the wind had increased to 10 - 15 mph. Just after shot #6, my chronograph blew over!!!, but what the hell, might as well launch the last one (#7). No adjustments were made for windage during the test, but I tried to squeeze off the rounds between gusts as much as possible.

So here is the end result:

Would anyone like to help intrepret the results? Looks to me like maybe start somewhere between #6 and #7 loads...?

In case there is any interest, velocities were as follow:

1) no data
2) 2787 fps
3) 2825 fps
4) 2841 fps
5) 2858 fps
6) 2867 fps
7) chron0 blew over, no data

 

[dragonjr45]

Re: Ladder Test - Analysis

6 and 7 look great, but really I would try 4,5,6,7 again on a calmer day, and I like to let the barrel cool between every shot just so it doesn't get hot by the end.

If your not running into pressure signs yet, I would consider upping the charge a little to see how big that node is, since 6 and 7 looks so good.

 

[2clicks]

Re: Ladder Test - Analysis

Don't let each round sit in a hot chamber either single load. I know varget is suppose to be temp insensitive, but u remove a variable that way. Fwiw I could give a rats ass about the left and right its the up and down/ verticle I'm looking to get together between two charges.For example if loads with 28.5 & 29 grs are side by side 3 inches apart on a super windy day I'm going to call that the sweet spot and take a closer look at those loads or one in between those weights.

 

[Jeffvn]

Re: Ladder Test - Analysis

I would re-run the test using numbers 4 to 7; I agree with 2Clicks, unless you ran into pressure issues, I would add another load or two on top for an new number 8 and 9, just to see how high the node extends. Left to right means nothing, with a ladder test you are looking for the verticle from shot to shot.

I always single feed these tests, but run two or three tests on the same sheet back-to-back to see consistency. I have a big piece of plywood that I use for this purpose. It does not blow around in the wind and gives me the room to set up multiple ladders at the same time.

Once you know that you are above your minimum acceptable velocity, you can leave the chronograph at home for ladder testing.

Jeffvn

 

[rymart]

Re: Ladder Test - Analysis

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 2clicks</div><div class="ubbcode-body"> Don't let each round sit in a hot chamber either single load. I know varget is suppose to be temp insensitive, but u remove a variable that way. Fwiw I could give a rats ass about the left and right its the up and down/ verticle I'm looking to get together between two charges.For example if loads with 28.5 & 29 grs are side by side 3 inches apart on a super windy day I'm going to call that the sweet spot and take a closer look at those loads or one in between those weights. </div></div>

I single loaded each round and waited about 2 minutes between shots for the barrel to cool off. Had a faint/slight ejector mark on #7. There was a definite increase in wind between shots 5 and 6.

 

[ryhag1]

Re: Ladder Test - Analysis

Heres a great article that explains a lot.

http://www.6mmbr.com/laddertest.html

 

[okiefired]

Re: Ladder Test - Analysis


http://optimalchargeweight.embarqspace.com/

okie