Reading a Ladder Test?

[RonAKA]

I did a ladder test in a velocity area (3400-3500) that appeared to be of interest in earlier ladder testing. I used 0.2 grain steps, and shot three shots at each load step. Following were the results for the three bullets tested. Distance was 300 meters.

So, based on these results what loads would you choose? I'm thinking as follows:

Bart's 68 - 34.4 grains, 3420 vel
Berger 68 - 34.1 grains, 3415 vel, or would you go out further to 3450?
Berger 69 - 34.3 grains, 3415 vel

 

[rocketron]

i think i would retest the 34.2....34.4 berger 68 gn....it seems to have the least change in elevation (hard to tell w/yellow over it)and about 10 fps differance in velocity.....if i'm reading it correctly. you said three shots at each load but i see five markers

Ron

 

[RonAKA]

you said three shots at each load but i see five markers

Ron, each marker is the average of three shots both for velocity and for elevation. Each marker represents one load level. On an individual shot basis I was not able to relate velocity to elevation. It was a very calm day and quite foggy. At 300 meters I just could not see each bullet hole in my 24X scope.

 

[rocketron]

okay...long day at work.......five loads w/three shots of each......still like the 68 gn 34.1 to 34.3 area

Ron

 

[necchi]

My take on the Ladder is to choose the best charge that rep's the least amout of variation or just prior to a change, you want the fastest/highest prior to the change, or at least in the flat line area
So you can be looking at your graphs and see the bergers are both nice at 34.4.
Something's happening with the Barts,,but it looks like less than a 1/2 inch variation.
Also very important is , How did the actual groups look on the paper target?
I'd take the graphs as a guide but little more and place more value on the end result,,the group.

I guess I'm not a pro, but my simple take on barrel harmonics/vibration is there is generally a "range" that works well and not really 1 designated carved in stone spot, environmental variations alone can be critical in and part of finding that range or zone. So you want somthing that can take the variables and not be constantly pushing one side or the other of that "range".
Know what I mean? Am I way off here or,?? ???

 

[RonAKA]

I did my loading today and went as follows:

Bart's 68 - 34.4 grains. That was the easy one. I had a 0.331" group (vertical only) at that load at 300 meters. Actual group was only slightly larger.

Berger 68 - 34.3 grains. Was harder to decide. The vertical group at 34.4 was only slightly larger than the Bart's at 0.369". Again similar to the Bart's the overall group was not much bigger. However, I was swayed by the graph, and decided to move 0.1 grains back to the flatter position.

Berger 69 - 34.3 grains. Hardest to decide, and just kind of went with the trend. The 34.2 load was identical to the Berger 68 in vertical. The 34.4 group had vertical issues although the average was right in line. So I split the difference.

The interesting part is that while I'm kind of splitting hairs on charge, all three of these bullets seem to like essentially the same velocity.

 

[RonAKA]

Tested the three loads this week at 100 meters. For reasons I don't understand the Bart's 68 was the fastest with the extra 0.1 grain of powder. In previous testing with the same powder charge the Bart's was the slowest by quite a bit. The extra speed did not seem to agree with the bullet and the three 3 shot groups averaged 0.369, with a best group of 0.238. I had expected better.

The two Berger bullets at the selected load look very promising, with the exception that I'm getting 1 flyer in 9 shots. Results as follows:

Berger 68 - 0.132, 0.145, 0.540
Berger 69 - 0.126, 0.227, 0.559

The flyer was in the third group both times, and was mainly a vertical issue (high). Any thoughts on what might be causing it? I know on one of them I did not get a real clean trigger pull, but was sure I was not off by as much as it turned out to be.

Also any thoughts on how narrow a sweet spot can be? The Berger was only off by 20 fps and seemed to be out of the sweet spot. In powder we are only talking 0.1 grains, or perhaps even less.