580 yard ladder test 6.5 RPM

[diderr]

Did my first single shot ladder test in a long time. Am I safe to say 60.5 is the middle of a node?
Caliber: 6.5 RPM
Powder: 7828 ssc
Charges: 57-61.5 in .5 grain increments
Primer: fed 210
Case: Weatherby
Book max; 61.2
Distance: 580 yards
Wind: 20-30 mph gusts. Mostly tail wind

Upper and right 59 was my sighter shot

 

[IHFarmer07]

Hmm windy conditions doing a ladder makes this a bit hard.

You can try it again with better conditions or stay with what you have. With the last option, I would look into 58-60.5 area.

 

[diderr]

It all looks promising in that range. 61.5 gave me a plunger bur. Everything below that was all golden pressure wise. And if 7828 is as sensitive to temp as they say I’d rather stay lower. This is a hunting rifle and probably won’t get shot much above 70 degrees ambient temp.

 

[IHFarmer07]

It all looks promising in that range. 61.5 gave me a plunger bur. Everything below that was all golden pressure wise. And if 7828 is as sensitive to temp as they say I’d rather stay lower. This is a hunting rifle and probably won’t get shot much above 70 degrees ambient temp.

Yeah, you need to stay a little below pressure in your gun.

Try 3 shot groups in between the weights of 58-60.5 in .3 grain increments On a good ladder target where you can see out of those groups the poi change as you go up.
Or search for load development targets and print you own.

 

[diderr]

Thanks!

 

[RegionRat]

Kinda loose and hard to say. Probably too windy.

The waves start at 59 and go to 61 when you imagine the vertical uncertainty of any three steps in a row. I would keep trying.

Suggest what was said above, or repeat with finer steps in less wind. Good Luck.

 

[diderr]

Going to head out tomorrow and probably test 59-61 and get chronograph data at 60.5. Going to do 3 shot groups. Now should I shoot farther? Maybe 1,000? Forecast is showing 15mph (rare to have a calm day where I live in windy Wyoming )

 

[IHFarmer07]

Going to head out tomorrow and probably test 59-61 and get chronograph data at 60.5. Going to do 3 shot groups. Now should I shoot farther? Maybe 1,000? Forecast is showing 15mph (rare to have a calm day where I live in windy Wyoming )

I’d try it at 100 then move out farther.

Usually when I do my 600-650 yard ladders I test what I think is a possible load from the 600-650 ladder at 100 yards in .3 increments at 100.
I then judge the groups and then adjust the seating depth.

Watch these videos as I have several times and I use Ryan’s way of load development.

 

[Feniks Technologies]

IMO, "safe" is going to be a hard result on a test like this. Especially if you're not tracking velocity on the shots.

For example, lets take 58 and 58.5. I'm going to make up numbers for simplicity sake:

Lets say both charges have an ES of 30.

58 runs 2900 and 58.5 runs 2950fps with a 109 Berger

58.0 = 2885-2915
58.5 = 2935-2965

Now lets look at the scenario where you took one shot each @ 600yds and the 58.0 was on the high and 58.5 was on the low

2915 = 3.3mrad or 71"
2935 = 3.2mrad or 69"

So, lets also say the rifle is a .5 moa shooter/rifle combination.

That's just over 3" @ 600yds.



So, that means, without a chrono to tell you what the individual speed was on each shot, its extremely possible your two rounds were fairly close in velocity as well as have an overlapping cone of precision.


Long story short.......a ladder test with single shots + no chrono + overlapping precision cone = not reliable.

 

[BuildingConceptsllc]

I'm not understanding how this test could give you any usable results? I would do 3 shot tests at 100yds with .3 gr increases and a chrono. If not at least that, you're just wasting your time and components.

 

[diderr]

Thanks for the help guys!

My biggest thing is I have a Magneto chrono so I can’t do load development and chrono at the same time. My theory is at 600(ish) yards it will show me accuracy node and where the velocity tends to stabilize on charge weights. Got the idea from benchrest shooters on Accurateshooter. And a couple YT videos.

And also shows me my guns pressure window. Basically to limit the need to have to tear down multiple rounds if pressure gets too bad. Or atleast a starting point.

I loaded lastnight 3 rounds loaded of 59, 59.5, 60, and 61
I got 3 rounds plus chrono rounds loaded at 60.5
The chronograph loads wont be shot in the dirt as I can just zero my RMR at 50 yards at the same time. Doesn’t matter if the weight of the chrono throws off harmonics or POI a little

 

[Feniks Technologies]

Use caution. You might be cross contaminating two things:

- Velocity “flat” spots that don’t exist and are not a valid form of load development.

- ladder tests for POI comparison which is using positive compensation theory. This hasn’t be ruled out as not valid and is what most F and BR shooters reference when talking about “flat” spots. It’s not a velocity flat spot, but a POI flat spot. This is also subject to the situation I described above.


It has become increasingly common for shooters to misunderstand what “flat” spots are that have been talked about for years by F and BR shooters. It’s not velocity related.

 

[diderr]

IMO, "safe" is going to be a hard result on a test like this. Especially if you're not tracking velocity on the shots.

For example, lets take 58 and 58.5. I'm going to make up numbers for simplicity sake:

Lets say both charges have an ES of 30.

58 runs 2900 and 58.5 runs 2950fps with a 109 Berger

58.0 = 2885-2915
58.5 = 2935-2965

Now lets look at the scenario where you took one shot each @ 600yds and the 58.0 was on the high and 58.5 was on the low

2915 = 3.3mrad or 71"
2935 = 3.2mrad or 69"

So, lets also say the rifle is a .5 moa shooter/rifle combination.

That's just over 3" @ 600yds.



So, that means, without a chrono to tell you what the individual speed was on each shot, its extremely possible your two rounds were fairly close in velocity as well as have an overlapping cone of precision.


Long story short.......a ladder test with single shots + no chrono + overlapping precision cone = not reliable.

That makes a lot of sense with the highs and lows of the ES spread with POI

 

[MarkyMark007]

My theory is at 600(ish) yards it will show me accuracy node and where the velocity tends to stabilize on charge weights.

how can you tell from 1 shot that you have accuracy node? what if you have at your 'flat spot' groups very big, but you dont see them because you shot only 1 shot, and now you read ladder totaly wrong?
and how can you say something about velocity, but you didnt measure it?

go through ladder 5 times and you will see real flat spots, not imaginary.

 

[diderr]

I did 3 shot groups at 625 yards today. 59, 59.5, 60, 60.5, 61. I used 60.5 as my sighters moved my scope down and left after the upper right group. Both groups with the 60.5 yielded .6 moa. ES was 10 at 2,948 average. My 1 shot ladder was trying to kill 2 birds with one stone. Give me a safe pressure window and maybe give me a hint at what to look at.
I decided to stay with 60.5
This is a hunting rifle and .6 Moa off a bipod and rear bag is plenty for me. These are loaded at max COAL for the mag. I can easily visit seating depth next

I’ve been chasing a load for this gun since I’ve had it. Started with us869(horrible powder) then sourced 4 pounds of the 7828. With the barrel life of this round is like to get some good practice and a few animals on it . I have a 28” proof waiting then it will become a 6.5-284