Interpreting Ladder Test

[Woolsocks]

first test loads in my new 280AI build. Starting from 53.5gr H4831 and going up to 58gr. Shooting 3-shot groups at 200 yards.

Here’s an overlay. As you can see, the groups start at 53.5gr just under the point of aim, go down slightly, slide right, then go down again until you get the last (58gr) group at the bottom right.

trying to get my head around the left-to-right shift. What does it mean? Am I seeing a node in the 56.5-57.5gr range?

happy with the accuracy from this load, most of these groups are 1/2moa or better. Just trying to figure out what this sideways shift means, and if I can use this data to guess at a node. The chrono is giving me very consistent velocity changes of 20-30fps between load steps, so I’m not finding a node from chrono data.

 

[rustyinbend]

Is this a brand new barrel, or has it been broken in and shooting tight groups before this? Just curious ...

 

[Harman117]

My $0.02: Velocity nodes aren't real, speed is a direct linear relationship with amount of powder. Everything you know is a lie. Your test means nothing and is well within the noise/typical variance of the system.

Pick the speed you want and shoot.

Give this a listen when you have the time:

 

[ShtrRdy]

The 55 and 55.5 shots have quite a bit of horizontal so I would guess that the barrel vibration in the horizontal direction is transitioning between the left and right "sweet spots".

later ..... I will mention that the test you did is more along the lines of an Optimal Charge Weight Test. I agree with your observation of exploring the 56.5 to 57.5 grain area more.

 

[ShtrRdy]

My $0.02: Nodes aren't real, speed is a direct linear relationship with amount of powder. Everything you know is a lie. Your test means nothing and is well within the noise/typical variance of the system.

Pick the speed you want and shoot.

I respectfully disagree

 

[Harman117]

I respectfully disagree

Perfectly fine, I remember when I use to waste time doing these "tests" too.

OP the easiest way to see for yourself is to perform the test again, exactly the same, and I'll bet the results don't repeat like you would expect.

 

[Doom]

Shooting a ladder is not shooting groups. Ladders are shot to determine vertical dispersion and usually shot 1 shot/load on a target. If shooting for group size you typically will shoot a charge on each target. As for chronograph data if you are looking for flat spots they are not a function of the charge but of random deviations in the data.

It looks like you do have something in the 56.5 to 57.5 but being shot at only 200 yds it's might not be that wide.

The horizontal shift is puzzling but you mention that it is a new build. If this is a new barrel and you have less than say 50 rounds it might just be settling in. You didn't say anything about the barrel weight or how you fired the rounds so one thought is barrel heating and possibling the barrel not free floated. It is also possible you have scope mounting issues.

I would not rule out the possibility that the shift is due to the change in charge weight. I would suggest you try something like loading the whole range, one shot per charge and reshoot the ladder highest charge to lowest and see if the pattern repeats.

 

[Seymour Fish]

My $0.02: Nodes aren't real, speed is a direct linear relationship with amount of powder. Everything you know is a lie. Your test means nothing and is well within the noise/typical variance of the system.

Pick the speed you want and shoot.

Give this a listen when you have the time:

Agree 100% and second your position that all Benchrest champions, and F-Class champions are liars. Only Hornady can be trusted to tell us the truth, and nothing less than 5000 rounds can give us the Statistical Validity we must worship. I, however, don’t believe you Sir, are Worshiping up to my standards, thus I beg you to Worship the God of Hornady Harder. Surely you can try harder to infiltrate every discussion amongst the great unwashed, and bring them All around to the Modern Lockstep Way, for anything less is intolerable. Commit, my son, to going the whole dollar. Your .02 cents is unconvincing.

 

[Harman117]

Agree 100% and second your position that all Benchrest champions, and F-Class champions are liars. Only Hornady can be trusted to tell us the truth, and nothing less than 5000 rounds can give us the Statistical Validity we must worship. I, however, don’t believe you Sir, are Worshiping up to my standards, thus I beg you to Worship the God of Hornady Harder. Surely you can try harder to infiltrate every discussion amongst the great unwashed, and bring them All around to the Modern Lockstep Way, for anything less is intolerable. Commit, my son, to going the whole dollar. Your .02 cents is unconvincing.

Oh I struck a nerve with someone this morning!

Like I said OP, shoot the test again, and see for yourself. Fire the test in reverse order, results should repeat, right?

Or keeping looking for "nodes" in small samples. It's your time and money

 

[Woolsocks]

Shooting a ladder is not shooting groups. Ladders are shot to determine vertical dispersion and usually shot 1 shot/load on a target. If shooting for group size you typically will shoot a charge on each target. As for chronograph data if you are looking for flat spots they are not a function of the charge but of random deviations in the data.

It looks like you do have something in the 56.5 to 57.5 but being shot at only 200 yds it's might not be that wide.

The horizontal shift is puzzling but you mention that it is a new build. If this is a new barrel and you have less than say 50 rounds it might just be settling in. You didn't say anything about the barrel weight or how you fired the rounds so one thought is barrel heating and possibling the barrel not free floated. It is also possible you have scope mounting issues.

I would not rule out the possibility that the shift is due to the change in charge weight. I would suggest you try something like loading the whole range, one shot per charge and reshoot the ladder highest charge to lowest and see if the pattern repeats.

Sure. Using three rounds of each charge weight is an attempt to weed out random data from a pulled shot, gust of wind, whatever. So think of it as three ladders overlaid.

The barrel is a proof carbon fiber pulled off a savage 110 ultralight I bought used with about 60 rounds of factory down it. So it’s broke in. Awsome barrel. Proof tells us these barrels are the same as any other barrel you’d buy from Proof so we can’t say “factory barrel” and throw up our hands

I’m mostly trying to figure out why the POI shifts to the right and down as the velocity increases. I’d have thought it would go in a more or less straight line up the paper.

Doubt the build, scope, barrel heating, etc has anything to do with it. Here’s an 8-shot group at 300yds with the 57gr load (with the scope adjusted so the POA=POI). No sideways movement with 8 shots of the same powder charge. I think we can definitively say that the barrel vibration is causing the right/down shift. Just trying to understand it..

 

[Chris1972]

In my experience a rifle will shoot good with any reasonable load if it’s built right. A smith who built a rifle for me told me step it up until I found pressure then back off half a grain and that’s the load. I thought he was crazy, until he was right. I’ve never had that experience with a factory rifle and only half of the ones chambered by a professional. I now pick a speed and do some simple seating depth testing. I’m sure there’s many out there but I’ve only found two gunsmiths who can build a rifle like that.

 

[straightshooter1]

Sure. Using three rounds of each charge weight is an attempt to weed out random data from a pulled shot, gust of wind, whatever. So think of it as three ladders overlaid.

The barrel is a proof carbon fiber pulled off a savage 110 ultralight I bought used with about 60 rounds of factory down it. So it’s broke in. Awsome barrel. Proof tells us these barrels are the same as any other barrel you’d buy from Proof so we can’t say “factory barrel” and throw up our hands

I’m mostly trying to figure out why the POI shifts to the right and down as the velocity increases. I’d have thought it would go in a more or less straight line up the paper.

Doubt the build, scope, barrel heating, etc has anything to do with it. Here’s an 8-shot group at 300yds with the 57gr load (with the scope adjusted so the POA=POI). No sideways movement with 8 shots of the same powder charge. I think we can definitively say that the barrel vibration is causing the right/down shift. Just trying to understand it..View attachment 8537990

Below is a pic showing the sine wave for barrel vibration as this is shot out of a high end gun buy a high end shooter and reloader (not me) using the same exact load. All that's being changed is the tuner setting effecting barrel timing to the harmonics. This very same sine wave has been produced in tests by others as well and I've seen it out of my less than high end gun too (just larger groups ) . Other than the obvious sine wave that can be seen, note the horizontal movement off the POA's that's also happening. The barrel vibration is actually spiral, not just vertical or horizontal.

The changes in powder charges resulting in different velocities where the projectile is exiting from different muzzle positions during the vibration. The more consistent/uniform everything is (e.g. the powder charge, ignition, release of the projectile, chamber pressure pressure, velocity) the position the projectile is released will be more consistent. . . and tighter groups, if the shooter is consistent too .

Like in the test below, it's best to shoot along a horizonal line when testing to make it much easier to interpret just what's going on.

 

[Woolsocks]

The barrel vibration is actually spiral, not just vertical or horizontal.

THANK YOU! That answers the question.

 

[MarkyMark007]

Below is a pic showing the sine wave for barrel vibration as this is shot out of a high end gun buy a high end shooter and reloader (not me) using the same exact load. All that's being changed is the tuner setting effecting barrel timing to the harmonics. This very same sine wave has been produced in tests by others as well and I've seen it out of my less than high end gun too (just larger groups ) . Other than the obvious sine wave that can be seen, note the horizontal movement off the POA's that's also happening. The barrel vibration is actually spiral, not just vertical or horizontal.

The changes in powder charges resulting in different velocities where the projectile is exiting from different muzzle positions during the vibration. The more consistent/uniform everything is (e.g. the powder charge, ignition, release of the projectile, chamber pressure pressure, velocity) the position the projectile is released will be more consistent. . . and tighter groups, if the shooter is consistent too .

Like in the test below, it's best to shoot along a horizonal line when testing to make it much easier to interpret just what's going on.

View attachment 8538077

so which spots are the best?
2-3 and 9; maybe 13-14 ?