Thread: 440m ladder test

Originally Posted by marky123

As far as I understand,a ladder test is the relationship between POI and velocity.If unsuitable powder charges are used then they are nowhere near their next or previous.If it is,then they are closer together,hence 3,4 and 5 are suitable charge weights in this instance.Further testing with those charge weights will prove or disprove that.Happy to be proved wrong.

Yup, but you are shooting single loads. How can you be sure the vertical dispersion is due to the load and not due to your shooting.

That is why I keep stressing 5 shot groups. If you can show me 5 shots of the same load, all on the same vertical plane, then I will be convinced.

The correlation between increasing load and increasing velocity is not completely linear.

The target you posted has vertical all over the place (some of the slower loads land higher etc), so it does not really show much. If you were shooting a whippy hunting barrel, that may have been due to harmonics causing the projectile to leave the muzzle at different points in the whip, but then you would struggle to shoot accurate groups at most time.

All things working well, you would expect to see poi climb as the charge weight increases. Where that climb becomes contracted for equal increases in charge, is likely to be a node. I am not seeing any of that on your target (based on poi)... I do however see a potential node if you look at the speeds.

2 questions:

1) what chrony are you using ?
2) rifle ? particularly barrel profile ? is it a noodle or something a bit more beefy like HMR ?

Originally Posted by ebf

Yup, but you are shooting single loads. How can you be sure the vertical dispersion is due to the load and not due to your shooting.

That is why I keep stressing 5 shot groups. If you can show me 5 shots of the same load, all on the same vertical plane, then I will be convinced.

The correlation between increasing load and increasing velocity is not completely linear.

The target you posted has vertical all over the place (some of the slower loads land higher etc), so it does not really show much.

Assuming the chrony and the shooter (not me) were working correctly and the conditions were good (there was no readable wind) then the test shows less POI dispersion and velocity between some shots to others.
You can reasonably presume that those charge weights are ‘good’ loads.We will then repeat the ladder test hopefully under the same conditions with a smaller variance of charge weights at the same distance.Hopefully some of those loads will be ‘good’.Then we will select a load and shoot groups with it to confirm.

If that works then we have found a ‘better’ load with 20 shots.

More charge weight is not linear with velocity,I haven’t said it is.
We will shoot some 3 or 5 shot groups but only when we have dialled in a ‘good’ load.