Thread: Interpreting a Ladder Test

Hi P38. To make it easier for me I numbered your shots. Statistically there are no patterns here, just data that says that ladder testing will not give you the information you are wanting.
Both ladder testing and the OCW method are intended to identify barrel vibration "nodes" as a means to reducing the effect of shot-to-shot variance in a given ammunition. My interpretation of this target is that other factors in your set-up are setting the overall group size, masking the information that the ladder test may otherwise provide. They will do the same thing for OCW testing.
My best advice if you are wanting to shoot smaller groups is to pass on ladder & OCW testing and shoot test groups with each type of bullet that are acceptable for the task you have in mind and hope that one or more of these meets your expectations, sticking with a moderate load for each, 7-shot minimum groups to get a bit of statistical significance. Good luck.

Originally Posted by Puffin

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Hi P38. To make it easier for me I numbered your shots. Statistically there are no patterns here, just data that says that ladder testing will not give you the information you are wanting.
Both ladder testing and the OCW method are intended to identify barrel vibration "nodes" as a means to reducing the effect of shot-to-shot variance in a given ammunition. My interpretation of this target is that other factors in your set-up are setting the overall group size, masking the information that the ladder test may otherwise provide. They will do the same thing for OCW testing.
My best advice if you are wanting to shoot smaller groups is to pass on ladder & OCW testing and shoot test groups with each type of bullet that are acceptable for the task you have in mind and hope that one or more of these meets your expectations, sticking with a moderate load for each, 7-shot minimum groups to get a bit of statistical significance. Good luck.

Puffin

Thanks for this.

I agree the ladder test really didn't tell me anything at the end of the day and the OCW may be too much at this stage.

However I like the look of the two loads I shot groups with the following day.

I'm using this load for hunting at moderate ranges, up to 300m.

I have access to a 200m range and will retest these loads in a week or two shooting some groups.

Cheers
Pete

I was trying a new powder for my .280 and every load from 53.5 to 58 shot into a 2" group the next 2 at 58.5 and 59 moved away appreciably, so I'm going to load 3 at 57, 57.5 and 58 and hopefully get good speed and a smaller group.

Two good things about 3-shot groups; they are cheap, and you're 30-40% through shooting a meaningful number of shots to draw some valid conclusions. Either or both of the 47.5gr loads may shoot very well as you say, and if it was my rifle and load development my next step would be to make those test groups you have planned 10-shot groups of each (same number as used in the ladder test) to confirm this and to see if one of these shows through. If you do please post and let us know.

Three-shot groups are popular. I know this. I don't mean to appear to be down on your efforts either. From personal experience drawing incorrect conclusions (not helped by insufficient data overlayed with some wishful thinking ) is a path to wasting a lot of time and ammunition further down the path of load development, something to be avoided.

Pick three of the shots at random from your 10-shot ladder test. Repeated sampling like that will show up a fair % of these samples as small groups. It says something about what sample size may be required to give an insight into the true "population" doesn't it ?