Ladder Test

adamsgt

adamsgt

Jerry Adams
Someone referenced a ladder test here recently and that inspired me to try one. Hadn't done one before. I was also trying out my chronograph that interfaced with my laptop to see how that worked. I loaded 10 rounds for my 6 Beggs LV gun. Use LT-32 powder and Berger column bullets. I started at 25.6 grains of LT-32 and went up .2 grains at a time to 27.4 grains. I'm not sure what I can learn from this except that 100 yds is probably too short a distance to get meaningful results. Comments gratefully accepted.

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There is more than 1 way to skin a cat, but this method has worked pretty good for me. I load mine .1 gr apart. Seating depth is usually .015 + from touching - that way I only have 1 way to go later on. Label cases 1, 2, etc. I try and keep it to 10 or so cases - otherwise it gets really confusing later on. Have two identical targets (I draw lines on mine about 1" apart). Hang one target and keep the other at the bench with you. I like 200 yds. Shoot 1 shot - then mark the location of that shot on your target at the bench. This is where the lines come in - makes it easier to see where that shot went. Mark the shot with #1. Repeat for all cases.
While shooting, I use wind flags (3) - but give myself roughly 2 hours of change. I don't have enough cahunas to do load development without flags. Days when it is a straight cross wind are the easiest, but you can't always pick those days. This will help give you the most forgiving load.
When you're done shooting (most of the times, while you are shooting) you'll notice when 3-4 shots that group really well and it is hard to tell where each one went. Compare your target at the bench with the actual shot target. Of those 3-4 shots find the midpoint of that powder range and that is my powder charge.
I then move to 100 yds and find tune with seating depth and shoot 3 shot groups. Confirm load with 5 shot group.

Again, others may have different ways. Take what you like from each one and develop your own system.
 
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adamsgt said:
Someone referenced a ladder test here recently and that inspired me to try one. Hadn't done one before. I was also trying out my chronograph that interfaced with my laptop to see how that worked. I loaded 10 rounds for my 6 Beggs LV gun. Use LT-32 powder and Berger column bullets. I started at 25.6 grains of LT-32 and went up .2 grains at a time to 27.4 grains. I'm not sure what I can learn from this except that 100 yds is probably too short a distance to get meaningful results. Comments gratefully accepted. View attachment 13767
Click to expand...

For what's it's worth, here are notes I pull from my "Gene Beggs" file when I want to refresh my memory on comments he's made about the 6mm Beggs that I also shoot.

6mm Beggs Load

The rifle is chambered with a [light-turn] .269 neck.

Fed 205M primers are used behind a load of ***26.5 grains of H4198 Extreme [Gene's powder of choice for the 6Beggs]*** for an average MV of 3380 fps. ***

This upper window load should be approached with care.

Bart's 68 grain Headhunter bullets were seated .015 off 'jam' (jam is .020 into the lands per Gene) 0r .005" into the lands** with light neck tension (.001”).

I have settled on .015 “off of Jam” as my standard.

Seat a bullet long in an empty but sized case.

Chamber the round and work the bolt up and down about three or four times, then extract the round.

Set the seater die to this standard and using a dial caliper, lengthen the stem .015.

This should put you just barely into the lands. GB

If I recall correctly, Gene's tunnel, where he does a lot of meaningful research, is only 100 yards long.
 
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abintx: That was exactly the same recipe I've been using for the 6 Beggs. However, since the advent of LT-32 and the Berger column bullet I thought I'd try those to see how they performed. I've only got one partial jug of H4198 but two of LT-32.

Apollo: I hadn't thought that a tenth of a grain of powder would make enough difference. But I haven't tried that at 200 yds. I'll have to see where I can try that out locally.
 
Jerry - you bring up a good point that I overlooked. On the load ladders that I do - I already know, roughly, what the charge is going to be. For example; 30 BR with 118's and H4198 I think it will be around 34.0ish - so I would start a little under that and go a little above.

If I was doing this for a rifle that I had no idea, I would expand that range and go in .2-.3 increments to get a rough idea (and also a max load based on pressure signs) then go from there with another ladder test in .1 changes or start shooting 3 shot groups. Hope this gives you a starting point on developing your own system for load development.

I added a copy of my load ladder target in case this gives you some ideas. The #'s at the bottom relate to the numbers you put on your cases.
 

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  • Ladder.pdf
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Dumb question:
Since, for a ladder test I assume that you are primarily looking at the vertical position of the holes in the target, why not level a target and have closely spaced aiming points, on a horizontal line, and shoot one shot each?
 
Boyd Allen said:
Dumb question:
Since, for a ladder test I assume that you are primarily looking at the vertical position of the holes in the target, why not level a target and have closely spaced aiming points, on a horizontal line, and shoot one shot each?
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Aaaah, not a dumb question at all but a great idea. That way you don't have shots stepping on each other. Now I have to add a level to my range gear. :)

This also works with what Apollo suggested as I knew the load was going to be in the 26.5 to 27.0 range.

The experiment with connecting my Kurzzeit chronograph to a laptop computer went well. The software packaged with the chrono recorded each shot and displayed the value in large numbers on the laptop screen and stored them in series that I defined and provided instant analysis of each string. A big hiccup though is that my laptop is older and the screen is difficult to see in daylight, even in the shade on the covered firing line. In order to be really useful I'll need something with a brighter screen. My ipad is more than bright enough, even in bright sunlight but lacks usb ports for connectivity. Also, I doubt the software would run on a mac operating system. Well, tablets are getting better and cheaper so there may be something in the near future that will work.
 
When I shoot my ladder test - I aim at the dot, but have the bullets impact roughly 2" below. That way I don't shoot out my aiming point and the bullets are easier to see through the scope to mark on the bench target. I don't hold for conditions- just aim at the dot and let the bullets fall where they may. I look for both vertical and horizontal. Although vertical is a bigger red flag. If I happen to pull the trigger on a push or let up, I will make notes of that on my target at the bench. If the rifle is close to/or in tune then that shot should "make sense."
 
adamsgt said:
Aaaah, not a dumb question at all but a great idea. That way you don't have shots stepping on each other. Now I have to add a level to my range gear. :)

This also works with what Apollo suggested as I knew the load was going to be in the 26.5 to 27.0 range.

The experiment with connecting my Kurzzeit chronograph to a laptop computer went well. The software packaged with the chrono recorded each shot and displayed the value in large numbers on the laptop screen and stored them in series that I defined and provided instant analysis of each string. A big hiccup though is that my laptop is older and the screen is difficult to see in daylight, even in the shade on the covered firing line. In order to be really useful I'll need something with a brighter screen. My ipad is more than bright enough, even in bright sunlight but lacks usb ports for connectivity. Also, I doubt the software would run on a mac operating system. Well, tablets are getting better and cheaper so there may be something in the near future that will work.
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The Windows tablet has a USB port and Windows 7, but you probably knew that - - -
 
Pete Wass said:
The Windows tablet has a USB port and Windows 7, but you probably knew that - - -
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I was talking about the ipad. I'm looking at an HP 1104 or an HP 3125. They're 10.1 and 11.6 screen respectively, have 9 hours battery life and 3 usb ports. They seem to be running about the price of two 1000 pack boxes of Berger column bullets. Actually less. the 1104 runs about $433 and the 3125 $475. They have led backlit screens. Going to try and look at some tomorrow.
 
Adam for me I start with 1 particular seating dept starting at Jam with a specific powder charge (low).
Then I take that depth and increase it by .5 grains for about 3-4 different charges. The last one being at the top of the load window I would use.
I do this with 3 shot groups.
Then I increase the seating dept and load the same variation in powder.
I keep the cases separated in some of the plastic loading boxes. Then I go to the range with them.
basically using 133 it would look like this... x=seating depth
x @ 28.5
x @ 29
x @ 29.5
x @ 30

x - .003 @ 28.5
x - .003 @ 29
x - .003 @ 29.5
x - .003 @ 30

x - .006 @ 28.5
x - .006 @ 29
x - .006 @ 29.5
x - .006 @ 30

And so on.

Pick your starting dept and load and work from there.
I shoot them in 3 shot groups then I look for the seating depth that shows the least poi change
I take that and try some 5-8 shot groups.
I think there is something similar in either Mike or Tony's book. One was different from the other but similar.

I use a target like this one.
 

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  • 100 yd. Target.pdf
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I do the same thing as Francis, but I have multiple horizontal lines and fire 3 3-shot groups and average them.
 
Maybe I've just been lucky, but my ladder tests look like stairs. There are ranges of charges with reduced vertical dispersion. When I plot vertical versus powder charge, there are stair treads where shots hit near the same vertical position even though powder charge is increased. Then there are stair risers where there is a big jump in vertical. The concept is to pick a charge in the middle of a tread, so that variation in powder charge causes little difference in POI.
 
Attached is a photo of a ladder test I ran. All groups are three shot groups except for the four on the right which are five shot groups. One thing I noticed is that I didn't write enough information on the targets. I should have written the rifle used, powder and bullet used as well as wind conditions. I used Otto shims to vary the seating depth by .005". The thicker the shims the closer to the lands or into the lands. Same point of aim used for all targets which is immaterial as to where it was. I had two shots loaded for foulers. Three shots loaded in my block with 51.5, 52.5, 53.5 and 54.5 clicks on my RFD powder measure with the same shim. Shot them from left to right on the target. Shim was changed and same charge settings repeated on the next target row down and then shim changed again and charge settings repeated on next set of rows down. I picked out seating depth that showed promise and charge setting that seemed to work for three shot groups and shot the four groups on the upper right set of targets with five shot groups. If I remember correctly when this was done I only had a Beggs probe set out for a flag and was trying to shoot when the wind died down to the last dot on the probe instead of the probe pegging out. Not a good time to do ladder testing, but when you have a match coming up, you have to shoot when you can.

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Ladder Chart

I'm confused to say the least. Some time back Boyd had a ladder chart he posted that showed all shots in a vertical line, and was a certain number of shots held at one point of aim. The process was to find the least amount of vertical, or horizontal dispersion of the small group of shots made. I believe he used 3 shot groups of 3ths. per group. I hope I explained this correctly, and Boyd will interact to this ladder chart. I'm working on load development at 300 yards, and hope this description is correct, as I plan on trying it this coming weekend. If I am wasting time here I do apologize. Thanks waynej
 
Right on!

mks said:
Maybe I've just been lucky, but my ladder tests look like stairs. There are ranges of charges with reduced vertical dispersion. When I plot vertical versus powder charge, there are stair treads where shots hit near the same vertical position even though powder charge is increased. Then there are stair risers where there is a big jump in vertical. The concept is to pick a charge in the middle of a tread, so that variation in powder charge causes little difference in POI.
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Keith you are absolutely right. I first stumbled on to this phenomena many years ago in Phoenix. I was there for the Cactus, trying to get my rifle in tune, performing a ladder test, increasing the charge .3 grains at a time watching the point of impact climb steadily as the load increased. Suddenly, I reached a point where the point of impact quit climbing. :eek: I could go on up as much as .9 grain and the bullets still went in the same hole. :confused: I didn't know what was going on at the time but I knew I was observing something very significant. It was many years before I fully understood what was happening. What I had accidentally discovered was what we now call "Positive compensation." And you know the rest of the story and understand it perfectly. :)

Guys, when MKS (a.k.a. Keith Sharp) speaks, listen carefully. He knows what he's talking about.


Thanks for sharing your time and knowledge with us.

Gene Beggs :)
 
Gene Beggs said:
Keith you are absolutely right. I first stumbled on to this phenomena many years ago in Phoenix. I was there for the Cactus, trying to get my rifle in tune, performing a ladder test, increasing the charge .3 grains at a time watching the point of impact climb steadily as the load increased. Suddenly, I reached a point where the point of impact quit climbing. :eek: I could go on up as much as .9 grain and the bullets still went in the same hole. :confused: I didn't know what was going on at the time but I knew I was observing something very significant. It was many years before I fully understood what was happening. What I had accidentally discovered was what we now call "Positive compensation." And you know the rest of the story and understand it perfectly. :)

Guys, when MKS (a.k.a. Keith Sharp) speaks, listen carefully. He knows what he's talking about.


Thanks for sharing your time and knowledge with us.

Gene Beggs :)
Click to expand...



If you adjust for the elevation due to velocity changes, you supposedly get a sine wave rather than steps. And that you want to shoot just on the down turn of that wave where the velocity variation tends to cancel out the barrel vibration (vibration pushes the POI downward as velocity pushes it up). Never tried it, though.
 
Is his method up to Benchrest Standards?

I guess I question if his method will yield single bullet hole groups. The way I go at it, I don't rest until I have one small round hole. If one shoots Score, they must have all the bullets in one small hole, as small as they can get it. You can't agg into a good Score agg.

Pete
 
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