Ladder test with BACO 409420M2

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TexasMac
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Re: Ladder test with BACO 409420M2

Post by TexasMac » Sat Apr 03, 2021 4:38 pm

OK Guys,

It seems I need to educate some of you about ladder tests & the benefit thereof, including some of you “naysayers”. BTW, ladder testing is also known as the ladder technique or “The Incremental Load Development Method”. Although apparently not well-known is the BPCR community, ladder tests are an acceptable and excellent way to help zero in on a specific bullet & load that the rifle likes. It’s a technique used by many smokeless precision rifle shooters & the benefits also apply to BPCR.

So you have a new rifle or want to try a new bullet. So where do you start concerning load development? Many of you use start with a load based on recommendations or one that results with a certain amount of compression, etc. You load up a few rounds & head to the range. If you’re real lucky the results are excellent (tight groups) & you’re happy. But in many or most cases the grouping is not as good as you’d like. So what do you do next - typically change the amount of powder – right? Load up a bunch more and head to the range again. Or maybe you load up a bunch for a match & wonder why they did not perform as good as you’d like. After trying different loads & possibly attending several matches you eventually settle on a load combination that you can live with. That’s a lot of effort, time & expense.

The ladder test is a way to identify one or more velocity “sweet spots” for a given bullet during one shooting session. I believe most of you are familiar with the term sweet spot concerning barrel vibration & the benefits of resting the barrel on the cross sticks at a specified location. There are also sweet spots concerning velocity which affects barrel vibration & accuracy. If you can identify them you won’t waste the effort, time & expense trying many different load combination.

To run a BPCR ladder test I 1st determine the required powder for minimum compression for a specific bullet & cartridge overall length. Starting with the minimum compression, say 0.035” or so, I proceed to load rounds by increasing the powder in increments of 0.5grs until the maximum compression is reached (0.300” in this thread example). Each round is labeled with the powder weight and shot in order starting with the minimum charge.

Under perfect shooting conditions and with no human error affecting the shot placement one might expect each subsequent bullet to hit slightly higher than the last one on the target due to the increased velocity – move up the ladder so to speak. But barrel vibrations are a very significant factor influencing the shot placement. Therefore the shot pattern may move up then stop for 2 or 3 shots or more prior to moving up again, which identifies a possible sweet spot. It’s common to find a couple of potential sweet spots in a ladder test given sufficient number of loads. A true “sweet spot” is the point the rifle doesn’t care about the powder charge weight or resulting velocities, as long as it remains within a certain range. The result of the ladder test technique is simply to pick a charge in the middle of the sweet spot group charge weight range. The selected load should be tolerant to minor variation in powder charge weight & other load component variations.

Once the potential sweet spots are determined then load up 10 identical rounds or so with that powder amount for each potential sweet spot & head back to the range to see which one results in the best accuracy. So in a couple of trips to the range you’ve identified the best bullet/load combination for your rifle.

For a lot more details & better description of ladder testing, including the benefits, see the following link: https://www.6mmbr.com/laddertest.html

Wayne
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TexasMac
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Re: Ladder test with BACO 409420M2

Post by TexasMac » Sat Apr 03, 2021 4:43 pm

bobw wrote:
Sat Apr 03, 2021 9:34 am
Do as you like as you will , but the use of a different target for each group or pair would give you instant visual analysis of the results. Looking at your targets for more than a few seconds would having me looking for the Tylenol. Bobw
Bob,

There's no group or pair. As noted, each shot is fired from a round that has 0.5gr more powder than the last shot. As Chris noted in my other ladder testing thread, it would likely be easier to interpret the data if I were to plot the results of measuring the vertical height of each hole from a given reference point.

Wayne
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Re: Ladder test with BACO 409420M2

Post by bruce m » Sat Apr 03, 2021 5:31 pm

cw50-70 wrote:
Fri Apr 02, 2021 2:41 pm
Wayne, 53 grains is my 40-65 accuracy load for BPCR.
this statement requires more detail.
there are so many different bullets out there that fill different amounts of the case that the information is in fact meaningless.
bruce.
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Re: Ladder test with BACO 409420M2

Post by VectorMan » Sat Apr 03, 2021 6:53 pm

Thank you Wayne. As always I enjoyed your information.

KA
"keep adding powder til it bloodies your nose and blacks your eyes, then back it off bout 5 grains."

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Re: Ladder test with BACO 409420M2

Post by TexasMac » Sat Apr 03, 2021 7:40 pm

kenny sd wrote:
Sat Apr 03, 2021 5:51 am
have you tried OE powder, and also what mix do you use, 1 in 16 or 1 in 20.
ordering mold 409420m2 now,
I use a 408400 BA,, I think the 409 will be tighter in my Shiloh 74.
I'll give it a try. Ken
Ken,
I cast the 409420M2 using 16 to 1 alloy since it has a money bullet nose profile and I have concerns about nose setback with softer alloys.

I have not used OE powder & this thread is probably not a good one to respond to that question. I see you started another separate thread asking questions about std Swiss vs Swiss cavier. I suggest you add you question about OE to that thread.

Wayne
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Re: Ladder test with BACO 409420M2

Post by Kurt » Sat Apr 03, 2021 7:58 pm

Wayne,

We all have our way to do things and the end results is what counts, but I have to agree with Bob. Looking at your test I have to go my way shooting at least 3 to 5 shots per load on separate targets. These two targets were with the .44-77 testing two different bullets. The left string was using a bullet from a Sage mould and the right string was shot with a BA bullet .430/520 not .330" three shots each just increasing the powder loads for each 3 shot groups and the bottom target was a fire for effect using the best ladder group ten shots. All the ladder loads were from the 200 yard line.
Again the end results is what matters.

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Re: Ladder test with BACO 409420M2

Post by TexasMac » Sat Apr 03, 2021 8:45 pm

Kurt,

Although your technique of firing 3 identical loads at the same targets then moving to the next target with 3 identical loads, etc. may work well for you it's definitely not what I & other consider as a ladder test (see my definition & also the link provided) Using your technique to cover the same range of loads I tested using 0.5gs of powder per load increment would have required 63 rounds vs my 21 rounds.

Wayne
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Re: Ladder test with BACO 409420M2

Post by Kurt » Sat Apr 03, 2021 9:06 pm

I look at it this way I like a 3 shot average per load and a 5 shot in my mind will give me a better picture what that load will do.
In the past I was in the bench shooting and I read a similar write up in one of the gun magazines ( this was before these one eyed monsters we now read ) and I tried it but in the end I went back to 5 or more shots per group. Besides it gives me trigger time working on control too. :D
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Re: Ladder test with BACO 409420M2

Post by Aviator » Sun Apr 04, 2021 5:55 am

I suspect that the risk you run by limiting yourself to 1 shot groups, is that you are making the assumption that each potential load will result in very small groups, very low extreme spreads of velocity, and that you never have a less than perfect trigger-break.

My experience is that this is not a valid assumption. I think Kurt's photo of his target with 3-shot groups shows this pretty well.
(Of course, my experience is limited to my relatively short 2 years of shooting black powder. Still, the roughly 6,000 bullets shot through the Shiloh 45-70 in that 2 years gives me some perspective.)

I think the concept of one-shot groups makes for an interesting screening experiment, and may point you to an area to explore.
But, I for sure would expand my horizon before settling on a load for long-range BPTR competition.

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Re: Ladder test with BACO 409420M2

Post by TexasMac » Sun Apr 04, 2021 9:57 am

Aviator

My following comments are not meant to indicate that Kurt’s technique does not work. But understand that Kurt is not running a ladder test. He’s changing his point of aim for each 3-shot group & measuring the 3-shot pattern spread. A ladder test uses the same point of aim for the entire test and looks for grouping of shots as the shot pattern moves up in elevation. BTW, there is a hybrid version load development technique that combines the ladder test with Kurt’s process but it requires significantly more shots.

For the hybrid version load 3 identical rounds with the same amount of powder. Then load 3 more with the next incremental amount of powder. I like using 1/2gr but Kurt used 1gr. Continue to load 3 rounds with increasing amounts of powder until the maximum powder compression is reached. Then fire all the rounds using the same point of aim. The result is having to load 3X the number of rounds and 3X number of holes in the target. At 200 yds it would be hell attempting to keep track of the hits via a spotting scope. Rather than 21 holes, my target would have 63 holes. Using 3-round groups separated by 1gr of powder would reduce the number of shots but still end up with trying to track 33 shots.

I don’t intend to debate the pros & cons of the various techniques. Other folks use other methods & my initial posting and comments are not intended to imply that my use of the ladder test is the best technique. It works well for me. And yes, additional testing is recommended once the potential sweet spots are identified. I usually load 10 identical rounds for the selected sweet spots and head back to the range for final testing.

Wayne
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Re: Ladder test with BACO 409420M2

Post by Distant Thunder » Sun Apr 04, 2021 10:51 am

All I can say is that some people have a very narrow view of things.

And I should probably explain to some who may not have gotten it, but my reading the bones thing was meant to be humorous. I was not impugning anyone's methods even though I choose to do things differently.

I understand the method used here I just choose to do it differently, apparently others do too. Thanks for "educating" us though.
Jim Kluskens
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Re: Ladder test with BACO 409420M2

Post by Distant Thunder » Sun Apr 04, 2021 11:11 am

Steve,

I had that same thought. Even when the load is fully developed it will likely be between 1.5 and 2 moa if the shooter is capable.

I don't put my faith in one group much less one shot. I can usually tell if a certain bullet is going to work with a certain powder with 15 shots or so and if so I'll also know which powder charge range to explore. Then there's primers, wads,compression and many other things to refine. Plus with groups you have a record you can refer back to.

It could be that with a 1/2 or 1/4 moa rifle you could shave some time off development, with BPTR I think you just have to put in the time.
Jim Kluskens
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A new age of tyranny dawns in the United States! If anyone is brave enough to say so they're destroyed by the BIG Tech branch of the Federal Government for spreading lies! "Reeducation" camps to follow!

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Re: Ladder test with BACO 409420M2

Post by TexasMac » Sun Apr 04, 2021 2:41 pm

A forum member suggested that a chart plotting the distance of the shot holes from a reference point might be a better way to visualize the possible sweet spots. So I worked up a quick one using the point of aim as the reference point. The horizontal axis is the shot number & vertical axis is the distance in inches from the point of aim. In this case one looks for the flatter portions of the graph where the shot-to-shot variance is minimized. As noted earlier, shot #3 is clearly the best with #18 a 2nd possible candidate.

Wayne

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Re: Ladder test with BACO 409420M2

Post by Aviator » Sun Apr 04, 2021 7:35 pm

Wayne:
I'm sorry if your feelings were hurt. That was not my intent.

Certainly I think that you should do your load development however you prefer!

There is probably no such thing as the perfect experiment. In most experiments there are factors which we ignore, even though we could control them. And there are factors which would be difficult or impossible to control. Usually we try to devise a process which turns out to be as insensitive as practical to the factors which we do not want to control. And usually the goal is to end up with data that has low enough uncertainty that the results are useful.

One point that you might give some thought to: It really is not necessary that all shots in a ladder test need to be on the same target. Shots can be on different targets, as long as there is an appropriate aiming point, and no changes are made to the elevation setting on your sight or scope. The resulting elevation with respect to the aiming point is what matters.

Carry on, I'm out, no debate.

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Re: Ladder test with BACO 409420M2

Post by TexasMac » Sun Apr 04, 2021 9:08 pm

Aviator wrote:
Sun Apr 04, 2021 7:35 pm
Wayne:
I'm sorry if your feelings were hurt. That was not my intent.
Carry on, I'm out, no debate.
You certainly did not hurt my feelings & I did not feel that you intended to do so. I apologize if my response sounded that way. BTW, my "not debating" comment was meant as a general comment to everyone so as not to expect me to respond to differing opinions. I should have made it clearer that It was not intended just for you. Please carry on and don't hesitate to make you opinion heard. I expect and appreciate differing viewpoints although I may not agree with some of them. :lol:

Wayne
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