Ladder tests

[ReloadKy]

How many of you reloaders use ladder tests? What do you find to be the most useful in ladder testing?

[Dufus]

Ladders are good if you have the distance.

I prefer OCW. Again, if you have the distance.

[std7mag]

I do ladder.
Depending on cartridge i either do 100 yards, or 200 yards.
I go from start upwards 0.3 gr per round.
Look for 3 closest vertically. ( note, there may be more than one set)
I number the shots after 3 rounds on my target.
Middle of 3 closest vertically is your powder charge.

[Mobuck]

I've never used a ladder for loading anything but they work fine for accessing places you can't reach from the ground.
Seriously, I load to manual max or a predetermined velocity level. When I reach velocity and accuracy that fits my needs, I stop.

[hdwhit]

ReloadKy wrote:
How many of you reloaders use ladder tests?

Please explain what you mean when you use the term "ladder test".

[hounddawg]

for long range load development I use Erik Cortina's 100 yard method


for analyzing the targets I use a program called Ontarget, it allows me to shoot several groups or targets separately then to overlay them as a single group. That accomplishes the same results as the OCW method except it is much easier to accomplish. Here is an example from a single target with the 4 groups overlayed to get a picture of all 40 shots in reference to the bull. It can also import the data from multiple targets onto one. The upgraded 34 dollar version is needed for target analysis of high shot count virtual groups from multiple targets

[1stmar]

You need more than 100yds for a ladder test or ocw.

[hounddawg]

You need more than 100yds for a ladder test or ocw.

The farther out you shoot from 100 the more you increase the chance of wind/mirage/shooter error affecting the test. Factories and international champion shooters develop at 100 yards, even for long range. I think I will follow their lead

I only have a few plastic club level ribbons so don't take my word for it but the link I provided above was for a method developed by Erik Cortina who is a member of Team Lapua-Brux-Borden. He is a world class F-Class Champion.

A list of his accomplishments can be found here

http://www.lapua.com/en/lapua-team/l...k-cortina.html

I would bet he knows a thing or two about load development

[1stmar]

Follow whatever lead you want. You wont see enough of a difference in poi with .3gr in rements for a ladder or ocw at 100yds. Didnt say you couldnt load develop at 100.
Did you ask eric if used a ladder or ocw at 100?

[ReloadKy]

Hdwhit by ladder tests I basically mean what std7mag described. Shooting 10 rounds with same point of aim at different powder charges to see if you can find a few that shoot close to each other vertically.

[hounddawg]

Follow whatever lead you want. You wont see enough of a difference in poi with .3gr in rements for a ladder or ocw at 100yds.

whatever you want to believe, then believe. I tend to put more weight behind peoples methods that have walked the walk on the path I want to follow

I can honestly say that since I started using Cortina's load development my score went from an average of 191 to a average of 193.5 starting from the first match I began using ammo that had developed using that method and I have not even had time to fine tune the primers yet on main rifle. The first target of the first match I shot a 197 which is my highest score ever

[ed308]

I use 10 shot groups and look for the nodes. It works and saves a lot of time and money. But you'll need a chrony, Magneto Speed or Labradar to track speed.

Here's a summary from the 6.5 Guys website:

I start 1.5 grains below my max load and load 10 shells ascending by .2 gr. So for the Swedemoor, 50.0, .2, .4, .6, .8, 51.0, .2, .4, .6, .8, 52.0.

Then I will shoot these over the chronograph and look for the nodes. A node will be a velocity flat spot where .4-.8 gr of powder doesn’t move the speedometer much. This example with Reloader 26 in my 6.5 Addiction with 140 RDFs, the flat spot is between 51.2 and 51.8 grains -velocity went from 3025-3033 fps. So, .8 grains of powder added a total of 8 fps. Therefore, the middle of my node is 51.5 grains.

Next I then load up 5 of the 51.5 grain load and shoot them over the chronograph and the extreme spread was 5 FPS. I have repeated this with H100V, H4350, 4831, 1000, Retumbo, RE 17,19, 22, 23, 26, wiN 760, 780, VV 160, 170, 560, 570 IMR 4451, 4955, 7828 and 7977. With all of these powders, 3020-3035 fps was an accuracy node without regard to the powder type.

Once I find the velocity node I load in the middle of it then fiddle with COAL until it shoots tiny groups with low low extreme spreads. You can have an accurate load at 100 yards that will not shoot past 600 yards because you have a high extreme spread. For me any extreme spread that is over 25 FPS is unacceptable no matter how small the group is at 100 yards. Even if I had a load that shot .1 moa at 100 yard yet had an ES of 30, I wouldn’t use that load for a match. I would take a .3 moa load that had a sub 10 fps extreme spread any day of the week because the load will not start to spread vertically past 600.”

http://www.65guys.com/10-round-load-...t-ladder-test/

[hounddawg]

ed I use a similar method but just use 3 shot groups for initial testing to find flat spots on my .260 loads. When I go to bullet seating depth I use 5, then when I refine down to primer brand I shoot 10 per brand/type. For my .223 for loads that will not be shot beyond 300 I will no longer bother to chrono. The ES and SD will not matter enough to be worth shooting off a bench for. I much prefer prone

[1stmar]

LoadKy you can load develop at 100yds just not using an audette ladder approach. See this link: http://www.6mmbr.com/laddertest.html. It recommends 300-500 for stage 2. Dan Newberrys approach of OCW can probably be done at 100. Its goal is to remove flyers and allow for variations in components (powder, primer, brass) and technique without affecting group size. It wont necessarily be the tightest group just the most consistent in theory. There are other approaches as suggested, ed308 is a similar theory to ocw where you find a sweet spot.

[hounddawg]

LoadKy you can load develop at 100yds just not using an audette ladder approach. See this link: http://www.6mmbr.com/laddertest.html. It recommends 300-500 for stage 2. Dan Newberrys approach of OCW can probably be done at 100. Its goal is to remove flyers and allow for variations in components (powder, primer, brass) and technique without affecting group size. It wont necessarily be the tightest group just the most consistent in theory

nice article but could you explain what the method in the article does that testing of velocity ES and SD does not do at 100 other than adding in shooter error and environmental factors ?

[David R]

I found it works for me @ 100 yards with my 223.

I fire 5 shot groups @ 100 yards .2 or .3 gr apart starting 2 grains below max. I crony the loads.
Looking at the groups, they sort of make a part or whole sine wave. Pick the lowest group and go from there. It seems the lowest groups have the lowest SD.
Changing primers has moved the powder charge up or down .5 grains for a similar result.

I did this because I had some pull down 4895, now knowing anything more about it.

I was not a believer until I tried it.

David

[old roper]

David, How you find max load?

[David R]

Looking in all the manuals, I figured 25 grains was max for IMR 4895. I then chronographed the loads starting at 23. I did not reach factory published velocity for a 55 grain bullet (3200). I found a sweet spot a little over 3,000 fps and stuck with it. It takes almost 26 grains to get to 3200.

I had 500 Federal MATCH small rifle primers when I did the test.
I ran out and switched to RP small rifle. I re did the test and ended up with 1/2 grain more for same POI, group, and velocity.

I only shoot 100 yards off hand at paper, so Max Velocity was not important as group size.

I loaded the last 1,000 rounds in the 8 lb jug.

David

[old roper]

Thanks for getting back.

[fourbore]

Originally Posted by ed308

I use 10 shot groups and look for the nodes. It works and saves a lot of time and money. But you'll need a chrony, Magneto Speed or Labradar to track speed.

Here's a summary from the 6.5 Guys website:

I start 1.5 grains below my max load and load 10 shells ascending by .2 gr. So for the Swedemoor, 50.0, .2, .4, .6, .8, 51.0, .2, .4, .6, .8, 52.0.

Then I will shoot these over the chronograph and look for the nodes. A node will be a velocity flat spot where .4-.8 gr of powder doesn’t move the speedometer much. This example with Reloader 26 in my 6.5 Addiction with 140 RDFs, the flat spot is between 51.2 and 51.8 grains -velocity went from 3025-3033 fps. So, .8 grains of powder added a total of 8 fps. Therefore, the middle of my node is 51.5 grains.

Next I then load up 5 of the 51.5 grain load and shoot them over the chronograph and the extreme spread was 5 FPS. I have repeated this with H100V, H4350, 4831, 1000, Retumbo, RE 17,19, 22, 23, 26, wiN 760, 780, VV 160, 170, 560, 570 IMR 4451, 4955, 7828 and 7977. With all of these powders, 3020-3035 fps was an accuracy node without regard to the powder type.

Once I find the velocity node I load in the middle of it then fiddle with COAL until it shoots tiny groups with low low extreme spreads. You can have an accurate load at 100 yards that will not shoot past 600 yards because you have a high extreme spread. For me any extreme spread that is over 25 FPS is unacceptable no matter how small the group is at 100 yards. Even if I had a load that shot .1 moa at 100 yard yet had an ES of 30, I wouldn’t use that load for a match. I would take a .3 moa load that had a sub 10 fps extreme spread any day of the week because the load will not start to spread vertically past 600.”

http://www.65guys.com/10-round-load-...t-ladder-test/

This is both very interesting and totally different from my 6.5 sweed testing. I do not plan to shoot beyond 200. But - this is very interesting (to me) approach. I never heard of a powder charge velocity node. I think I can try and apply some of this to my shooting.

This is a lot of work or a lot of fun, huh? I have only tried 4831. The old guns seem to like the 160RN. Not a long range bullet. Lucky, I dont need that. I may need to try a modern gun from our friends in Finland.

[Unclenick]

Test ladders (from the fact POI tends to climb as charge weight is increased) are a good way to identify load sweet spots, but it is also good to be aware there is more than one influence and effect to watch out for.

The velocity nodes were noticed long ago by Creighton Audette (the term Audette Ladder comes from his advocating their use in the 1980's) and Randolf Constantine and others. However, not all velocity nodes necessarily produce the best accuracy, even if they do tend to produce "better" accuracy than being off such a node. Dave Milosovich, writing in the Precision Shooting Reloading Guide (1995) offers an example on pages 90-91, firing 20 rounds in 0.2-grain increments that seem to exhibit stalling velocity increase with charge in two places occurring about 1.6 grains apart (follow the "Brief Overview…" link in this article). That's not very far apart. The 6.5 Guys advocate for a 10 shot load workup method based on the same increments showed two such spots within just 10 shots (about half as far apart). Here's a graph I made based on the data in their video at that link.



I've had individual sweet spots wider than the distances between these velocity nodes before, so something seems at least incomplete if not actually amiss. Here's what I think it is:

Checking in QuickLOAD it becomes apparent the velocity node spacing tracks the barrel time differences predicted by Chris Long's pressure waves in his Optimum Barrel Time theory. This theory is about the barrel distortion effects of pressure wave traveling at the speed of sound longitudinally in the steel. These waves were first spotted by Dr. Lloyd Brownell and are reported on pages 19-24 (30-35, as Acrobat counts them) of his 1965 study of absolute pressure in a Springfield '03 rifle. If a wave happens to be constricting steel near the throat when the gun's peak pressure is reached, it can raise the peak pressure and velocity a small amount. As charge weight is increased beyond that point the wave simultaneously has its phase relationship to the throat changing and widening, this can rob the cartridge of the expected increase in velocity over the next several increments of charge increase. Conversely, it will cause pressure to rise more than expected when the wave is changing phase on the other side of its peak.

So, a velocity flat spot can be found and had and that's all useful as it stabilizes the performance of the load velocity. But that's not the only thing going on in the system. At the same time, the barrel is bending an moving the muzzle. Below is an image of a ladder test group fired at 325 yards from a .270 Winchester sporter using the 140 grain Hornady SST bullet. It's one I helped a fellow identify the sweet spot for about a dozen years ago. I have put a spline fit into the plot so you can see there are apparent velocity nodes as he steps up through the load. This ladder was shot with 0.3-grain steps, to the 17 steps span 5.1 grains of powder, more than either Milosovich or the 6.5 Guys tried. Shots 3,4, and 5 don't look like much of a flat spot, but at 0.3 grains per step, it's almost a four-shot flat in the 0.2-grain steps the aforementioned experimenters used. By their reckoning, it's a great accuracy node. Looking at shots 11 through 16 you get a confusing group-like cluster, with #14 high. That is why there are several spline curves I tried out, eliminating shots as potential outliers to see what happened. However, even shot 14 is part of an average that is fairly flat.



To sort that out, I went to a polynomial curve fit to average out small velocity nodes and identify the biggest flat spot, which is the one due to muzzle deflection. I did that with the brown line in the plot below. I suggested he try all the apparent small flat spots, but none did great. The big flat spot between 13 and 14, though yielded very good results. When he tried that node at 100 yards (he couldn't get to the long range that day) he got two 3-shot groups of 0.3 inches that did not open at all when the two targets were overlapped. A 0.3-inch six-shot group, in other words. That's not a big shot count, but given the size, it limits how big a worst-case group could randomly be to within 0.42" or better 95% of the time. Not bad for a .270 sporter.


The reason I know the barrel deflection is responsible for one aspect of the flat spot is that barrel tuners work. They do nothing to velocity node locations that I've ever observed. But they can tune a barrel so its muzzle deflection matches a velocity node and that gives maximum accuracy quite nicely.

I suspect the reason seating depth changes can tune groups even smaller is it changes the phase relationship between the pressure wave and the barrel deflection by altering when the pressure wave initiates (when the bullet smacks into the throat). This allows you to tune to have both a barrel bend node and a velocity node that are synchronized, just as a barrel tuner may do. However, I'll warn you I have not proved this. I have a barrel tuner on one gun and I want to find if, once tuned optimally, I can make groups still smaller with seating depth tuning or not. If I can, my suspicion is wrong. If I can only make it worse, that is good evidence that my guess about tuning the phase relationship is right. With any luck, I'll have more on that later in the year.

Some guns may have issues arriving at the above nirvana by having problems with barrel contact with the stock or uneven loading of hangers under recoil and the like. So they don't all tune out neat and clean. Indeed, the complexity of the above relationships likely signals you pretty well that the system can be derailed by ill-tuning factors; especially those affecting consistency from one shot to the next.

One thing that has bothered me about all the single-string ladders is that you are often looking for variations a lot smaller than the standard deviation around the expected straight line fit is. I would fire several of them to check for a velocity node being real.

Finally, what distance can you shoot a successful ladder or round robin with? In my experience, this depends on how whippy the barrel is. If you have a free-floating ultra-light barrel of appreciable length, 100 yards can show you quite a bit of muzzle deflection. If you are shooting a benchrest gun like Audette was, it's may be difficult to make the effect out until you get to 300 yards, though Audette thought he could make it out at 200 yards, Randolf Constantine felt 200 was necessary. Cylinder rigidity increases as the fourth power of the diameter, so it doesn't take much extra barrel thickness to wind up with a lot less deflection. 100 yards won't show you loading errors that produce too high a velocity SD, but muzzle bending should be discernable with many sporters. Bottom line, as always: try it with your gun to see what you can tell from the test at shorter and longer ranges.

[hounddawg]

@ Unclenick

I agree with everything you just posted. One thing I like to point out though is like most things in life it all depends on the perspective. In my case I develop for three different yardages 100 - 300, 300 - 600 , and 600 +. I now develop for all three at 100. It has proven successful for me.

For 100 - 300 I only chrono the settled upon load before stretching it out past 100. The chrono stays in the truck for the devlopment.

For loads in mid and long range development I am convinced flat spots in the velocity trump small groups. Luckily groups with flat velocity and low SD's tend to group smaller naturally most of the time. Occasionally you get that one hole group in development with velocity all over the place but that seems to be the exception and not the rule. Once velocity is established the load goes to 600 for depth of seating and primer fine tuning.

I am switching out my 140 SMK's to Noslers in a few weeks so I will be doing some LR load tests and may post some with pics and velocity charts. I want to go try it at 1000 later this summer so I will be looking for a flat spot at the upper end of it's velocity curve

[Unclenick]

Originally Posted by hounddawg

For loads in mid and long range development I am convinced flat spots in the velocity trump small groups

Why settle for either/or, when you can have both simultaneously?

[hounddawg]

Why settle for either/or, when you can have both simultaneously?

because there are times when testing at 100 a load may have an ES of 20 and SD of 15 yet be a .4 group and on either side of that node ES and SD's will jump into the 20's. Farther up the ladder I might find a flat spot in the velocity where for several tenths the ES and SD's will be in the single digits but the groups may average .5 to .75. If that load was meant as a medium or long rang load I will choose the wider node with the flatter velocity. My 140 grain load is like that. I could load that ammo with a Lee dipper and keep the ES and SD below 15. I f that was a load meant for 100 - 300 I won't even bother setting up the chrono because out to 500 velocity deviation has only a minor effect of the vertical displacement

Groups are not everything unless you are shooting benchrest. My last 800 match my groups were horrible yet I snagged a 2nd place finish because my horrible groups were centered on the X ring and my competitors were all over the target. I did not have anything close to the smallest groups but they were consistent and centered.

I have found that for F Class matches that the standard deviation on the Y axis, the SD radius and the circular error probability give me a more accurate picture of what will happen during a 20 shot match than a simple group measurement.

If you are shooting benchrest buy all means load and develop for benchrest. If you are a hunter, develop for hunting, if you want to shoot F class then develop for it.

As always remember I do not claim to be an expert I am just like everyone else and I am just learning as I go. Trying things out and observing the results. My opinions and methods are subject to change. With that in mind my scores are considerably better than I was getting a year ago

[Unclenick]

I think you're still missing my point. You can make minimum group size occur at your best muzzle velocity flat spot. You can do it with a conventional barrel tuner by finding the velocity flat spot and then adjusting the tuning mass until you also have minimum size groups. Same with the Smart Stock tuner. You can also try different powders at the best velocity flat spot to see if one moves the muzzle deflection to be coincident with it. I remember one of the Gunsmiths at Gunsite saying he could often bring a gun in with a load just by trimming the barrel an eighth or a quarter of an inch, which is another option to try. You can try changing bullet seating depths. The bottom line is that you can have the best of both worlds and don't have to settle for choosing one over the other.