10 shot / Satterlee / ladder load development

[bboswell]

I love this concept and want to try it but IMO there is a variable it doesn’t account for.

In short, these technologies look for a flat spot in velocity which is perfectly logical.

Where I have a problem is that I know that no matter the components or methods there can be big swings in ES/SD.

Case in point: I need to start from scratch on an APR heavy target gun in 260AI.

Lupus brass is fire formed, necks turned, Redding bushing dies used with .002 tension.

Etc etc

The variable is ES.

I always record velocity while working up loads and even with equal components and prep things start with a big ES and then gets smaller and then opens again.

So who says the flat spot you see with 10 shot or a ladder is good info or just where you had two big ES numbers accidentally get close to each other?

[Closetohome]

Ladder testing focuses more on optimal barrel timing and harmonic nodes. The flat spots in velocity usually correspond to those nodes and I have generally found two nodes when load testing...one lower velocity and one near max. That flattening out I believe is more related to the bullet leaving the barrel in the most consistent and repeatable way...than it is to the powder burn. Usually lower ES/SD correspond to those nodes.

I know with today’s tightening supply of components the 10 shot method is a very good place to start as it can isolate some promising nodes.

Even if you go the optimal charge method, loading two rounds instead of 3-5 can give you a decent pattern.

[Stick1]

I love this concept and want to try it but IMO there is a variable it doesn’t account for.

In short, these technologies look for a flat spot in velocity which is perfectly logical.

Where I have a problem is that I know that no matter the components or methods there can be big swings in ES/SD.

Case in point: I need to start from scratch on an APR heavy target gun in 260AI.

Lupus brass is fire formed, necks turned, Redding bushing dies used with .002 tension.

Etc etc

The variable is ES.

I always record velocity while working up loads and even with equal components and prep things start with a big ES and then gets smaller and then opens again.

So who says the flat spot you see with 10 shot or a ladder is good info or just where you had two big ES numbers accidentally get close to each other?

Brent,

You are exactly right about the ES variable. It's about the most important component of a long range load. I also don't buy into the "flat spot" theory in velocity increases......at least not all of the time. With such a small sample size, and an unknown ES there is a lot left to interpretation. If you had a high ES of say 30 fps (which would very closely match a velocity step up with increased powder charge) and charge weight #1 was on the high side and charge weight #2 was on the low side.......you'd have a "flat spot" showing in your data which wasn't a flat spot at all.

We don't even focus on group size anymore until we have mapped out the charge weight node finding the lowest ES/SD. Once found, we will also test different neck tensions and occasionally a different primer to see if we can refine it any further. At that point, its usually just some small seating depth adjustments to map out the harmonic node and bring groups where you want them. It really doesn't take that much shooting as you pretty much know the window you are shooting for based on pressure testing.

On that note, big seating depth adjustments can throw everything out the window. Knowing the bullet you are shooting(typical/common jump distance it tends to like) and narrowing it down to a small .025ish window to start testing with will usually get you there without disturbing your numbers too much. We usually test seating depth in .003 increments.

Then there's always plan B - Jump .030, find the best charge weight node, screw an ugly tuner on the front and dial in tiny little groups

[bboswell]

Thanks Robert. Seems we are on the same thought process except I haven’t been adjusting seating in that small of increments.

[meltingfeather]

A good point, and one I've thought about.
Talking about SD on single-digit data sets would drive a statistician nuts!
I like Robert's method and am going to try it with a new set of Peterson brass for my APR.

[BLACKFINTURKEY]

Tagged.

As stated with components being hard to come by I’ve been considering this.

I really think where the 10 shot system can fail is if your chronograph isn’t accurate.

[bboswell]

Tagged.

As stated with components being hard to come by I’ve been considering this.

I really think where the 10 shot system can fail is if your chronograph isn’t accurate.

That used to be my thinking but now I have an accurate chrono and still don’t think you can get consistent results with a single shot at each charge. Robert did a great job of explaining why.

[viper3853]

Have you checked out this video.

Does a 50 shot ladder test. 5 of each charge.

https://youtu.be/9s9JymZntlk

Sent from my iPhone using Tapatalk

[meltingfeather]

Have you checked out this video.

Does a 50 shot ladder test. 5 of each charge.

https://youtu.be/9s9JymZntlk

Sent from my iPhone using Tapatalk

I do that but instead of shooting all 5 of each charge in a row I shoot the first one of each charge, then the second of each charge, etc.
I have to work the data a little more in Excel to get the same charge shots put together-- maybe I'm wasting time, but it made sense to me to control for barrel heating and fouling to some extent.

[meltingfeather]

Curious if others do this to and/or for thoughts about it.