Understanding ladder test results

[Ray P]

As I mentioned in another thread, I attempted my first ladder test yesterday. I made a few errors; the wind blew the diffuser screen off twice while I was looking through the scope, and I missed recording a reading.

Anyway, in spite of these (and I'm sure other) newbie errors, I did get the following result chart. I read this as having desirable flat spots in the two ranges circled.

Am I reading this correctly?


The two spikes are where I didn't notice the missing diffuser, and the gap is the reading i didn't take. If I can't recover the datum from the chrony today, I'll probably just reshoot the three.

Also I checked two references for the upper and lower limits for load; the Hodgdon 2016 manual, and Hodgdon's online load center (the powder H4350 is Hodgdon). the 2016 manual max is 54.3 grains. The online Load Center shows 55.5 gr as max, so I stayed 0.3 grains below lowest max listed.

Correction: the 55.5 gr max load is for a Barnes 130 gr SP. The max for the Hornady 30 gr SP remains at 54.3gr per the 2018, 2019 and 2020 manuals, and the current load center data.

 

[JFrank]

You seem to be reading it correctly although numbers alone don't make a good accurate load.
I would re-visit those areas in ( typo....01 or .02 grain) increments. one -two tenths is what I meant.

 

[AJC1]

Was this a single round ladder test or more. I know because it hurts me to do but for my testing I would want at least 3 shots each done twice on different days. There are a pile of variables and two charts from two different loading sessions would account for all of them. Solid statistics are driven by high volumes of quality inputs.

 

[Varminterror]

Which scale are you using?

The Satterlee method is pretty straight forward - flat spots are flat spots.

I do shoot triplicate instead of single shots per charge.

 

[Ray P]

You seem to be reading it correctly although numbers alone don't make a good accurate load.
I would re-visit those areas in .01 or .02 grain increments.

South Prairie Jim: I've been looking for an excuse to try out that old-school Ohler scale I picked up a while back. Did the first series on a RCBS Chargemaster at 0.1 grain increments. And I know that has it's own set of problems. Probably should use the Chargemaster for the 3 round re-dos.

 

[Ray P]

AJC1 and Varminterror: I did a single charge pass at 0.1 grain increments mostly because that's all the brass I had at the time*; all range pick ups over the last year or so. Two more passes at the same increment and measuring device would be very helpful in smoothing the chart. Also, it will smooth out variations from my chrony caused by inexperience with set up. This was my first time using the Chrony Master Beta. I had it on a good quality tripod from the local pawn shop, but there was much slack in the rig; too easily blown around by wind.

*Correction: my range pick ups, and a kind donation of nickel FC brass from Legionnaire via the pay it forward thread!

 

[Varminterror]

Did the first series on a RCBS Chargemaster at 0.1 grain increments.

Recall, the Chargemaster only has accuracy +/-0.1grn, meaning it doesn’t reliably resolve between 0.1grn increments.

 

[Ray P]

Recall, the Chargemaster only has accuracy +/-0.1grn, meaning it doesn’t reliably resolve between 0.1grn increments.

Agreed. Figured it might cause a false flat spot or two over at the most 3 increments, but that's why there needs to be secondary testing.

 

[AJC1]

AJC1 and Varminterror: I did a single charge pass at 0.1 grain increments mostly because that's all the brass I had at the time*; all range pick ups over the last year or so. Two more passes at the same increment and measuring device would be very helpful in smoothing the chart. Also, it will smooth out variations from my chrony caused by inexperience with set up. This was my first time using the Chrony Master Beta. I had it on a good quality tripod from the local pawn shop, but there was much slack in the rig; too easily blown around by wind.

*Correction: my range pick ups, and a kind donation of nickel FC brass from Legionnaire via the pay it forward thread!

Doing it three times would be even more important because the chace of getting the same load in the same brass is highly unlikely. Your 3 repetitions will show you the noise in your results. The results are far more unclear than your initial chart shows. I'm sure your aware your using a process for competition target using brass that massively increases your variables. Not impossible but much more difficult.

 

[JFrank]

Recall, the Chargemaster only has accuracy +/-0.1grn, meaning it doesn’t reliably resolve between 0.1grn increments.

Even so shouldn't it be close enough for what this gentlemen is doing ?

 

[kmw1954]

I would want at least 3 shots each done twice on different days. There are a pile of variables and two charts from two different loading sessions would account for all of them.

Agreed! I have also posted before that my testing starts with 12 rounds each at .03gr increments, many times I will start with three loading and then use two targets with each having 3 bullseye targets. I then fire 3 shot group of each load into a separate target. After all three loads have been fired I will mark each bull with the 1st round and then go back and shoot a second 3 shot group into the same targets and then after that is finishes I replace the target with a fresh one and repeat the process. So when I am finished I have 2 targets, each with 3 bulls and each bull will have 6 shots on it. I can then overlay the two targets and get a better full picture of how they are grouping.

If I find a load that did exceptionally well I will load that one again and then a load .01 on each side of it. Then if those loads do well I will load more and shoot them over multiple visits to compare and to determine if those results are repeatable.

 

[Ray P]

(...)The results are far more unclear than your initial chart shows. (...) Not impossible but much more difficult.

Understood. At this stage, and with these tools, I should not be expecting six-sigma results. Definitely realize now I need to make a couple more passes at the gross scale before tightening down on the finer increment testing.

 

[JFrank]

All you need is an area to work smaller increments, nothing Earth shattering that requires Lab precision at this point in time. Just find a load, heck you could do that with a 40 year old pact scale /dispenser combo.

 

[Varminterror]

Even so shouldn't it be close enough for what this gentlemen is doing ?

Absolutely, 0.2grn increments is more than “tight enough” to identify nodes.

But the experiment done here doesn’t reflect good science using the tools at hand - dispensing to 0.1grn increments when THREE OF THE THROWS could be the exact same weight based on the precision of the devise. Even when using 0.2grn increments, the Chargemaster might throw two of the same weight and pretend they’re different. We don’t use a tape measure when we’re cleaving atoms - using a +/-0.1grn device to dispense 0.1grn increments is an experimental error.

Which effectively is what raised my eyebrow at this comment:

I would re-visit those areas in .01 or .02 grain increments.

Frankly, if a loader has to chase down 0.02grn increments to find a node, there ain’t a node there.

We see this road being taken a lot - new reloader’s get mislead into a path stepping over dollars to pick up pennies. Despite actually owning gear which can dispense to 0.02grn, I would never use that resolution for load development or node identification. 0.2grn is more than tight enough. Maybe I’m too tolerant of “poor accuracy,” but when I deliver 1/4-1/2moa groups week in and week out with low single digit SD’s, and impact on 1/2-1moa targets out to 1200yrds in competition, with cheap brass, without annealing, no neck turning, no weight sorting of any kind, 0.2grn load work up increments, no seating depth tests... it really makes me question myself when I ponder all of the brass prep and load development voodoo I have done over the last 25yrs. If I were shooting short range benchrest, sure, I’ll pull out all of the stops, but for any other shooting application, I’d rather be shooting than tinkering.

ESPECIALLY when a guy is analyzing data based on single samples. Common standard deviation on any of those data points could completely reverse the findings.

 

[JFrank]

.01 .02 is a typo on my part.
My bad .2 grains is plenty close until you get to LR from there .1 is were im at

 

[Ray P]

South Prairie Jim, I need to add my own correction here: The mechanical scale i have is a Lyman/Ohaus M5; which has smallest marked increments of 0.1 grains. Per Ol' Doc (Ma) Soukup, my H. S. Chemistry Teacher back in the analog days, the best we can get by eyeball is half the lowest increment. Or in this case 0.05 grain.

 

[JFrank]

Although tuned to resolve '1 kernel ' I use an old beam scale for my 1k benchrest shooting no problems.

 

[Ray P]

So bluf, re-shoot the string twice more at even 0.2 increments using the RCBS. Then go to 0.1 increments on the Ohaus applied over a narrower band. Conveniently, that tosses the three bad points as they were all odd (52.3, 52.7, and 53.5 gr).

 

[Walkalong]

I do shoot triplicate instead of single shots per charge.

Me too.

 

[Varminterror]

So bluf, re-shoot the string twice more at even 0.2 increments using the RCBS. Then go to 0.1 increments on the Ohaus applied over a narrower band. Conveniently, that tosses the three bad points as they were all odd (52.3, 52.7, and 53.5 gr).

Are you shooting short range benchrest matches?

 

[JFrank]

Probably not with a 270 Winchester..

 

[Varminterror]

Probably not with a 270 Winchester..

My point, exactly.

 

[dcloco]

Not being smarty pants, but why look at velocity?

A ladder test is an accuracy test.

Shoot a ladder test at 300 yards and look for the 2/3/4 shot nodes. By all means, record the velocity, but quit worrying about velocity.......you are trying to find the accurate load???? yes? No?

 

[AJC1]

Not being smarty pants, but why look at velocity?

A ladder test is an accuracy test.

Shoot a ladder test at 300 yards and look for the 2/3/4 shot nodes. By all means, record the velocity, but quit worrying about velocity.......you are trying to find the accurate load???? yes? No?

I think he is doing a velosity test and not the classic ladder test for barrel whip timing. I see only a velosity chart not a target.

 

[Ray P]

Are you shooting short range benchrest matches?

No.