powder ladder??

[searcher]

I don't understand.... In order to adjust seating depth, don't you have to have a "pretty close" charge weight? How do you determine what charge to start with before you start with seating depth? I feel like a dog chasing my tail sometimes...

I do find it very helpful to work up a powder ladder with a particular powder approaching velocity somewhat close to where I want to run, with my depth set at soft jamb. Often-times, you just can't tweak velocity enough by doing depth adjustments to get the bullet to print as you want it to, if you are too far off on velocity to start. For example, if you are already soft jammed, your group looks like crud and you are running pretty much max velocity, you aren't likely going to get a "lights out" group with a hard jam. Your only options to dramatically (and safely) change the result is to reduce the load or back off the lands. If neither show significant improvement, I quickly switch to another powder. It is always a balancing act of velocity desired versus accuracy obtained.

I strive to have my bullet within .008" of the lands, preferably in them. So - I'll run my powder ladder with the bullet depth where I want it to be and stop when I get to the top velocity that I'm willing to shoot. Then I'll tweak depth a bit, then micro-ladder up and down a grain. Does that mean I started with my powder or my depth adjustments? I'm sure I'll get different answers there. In my mind, I started with powder. Another might say I started with depth. No wrong answers there.

 

[JFrank]

I’m a start with powder guy but I have a good idea where the bullet likes to be, so am I really starting with powder first ?
On the other hand guys that start with seating depth test first have an idea where the powder charge should be, so are they really starting with seating first ?

Jim

 

[Doom]

When shooting a Ladder on Target at 100yds you have to dissect what variables will be affecting the point of impact (POI) and consider the effect those variables on the POI. Velocity as it affects the built drop due to gravity is almost nothing. A 100 fps variation in most centerfire cartridges is going to affect the POI by less than a caliber. The largest variable in terms of impact at that range is the line of sight/flight path that the bullet leaves the barrel. This is primarily determined by where the barrel is pointing in its vibration cycle and velocity of the barrel that is perpendicular to the bullets velocity. This is a function of the barrel vibration frequency and the barrel time which is a function of velocity. When the powder charge is burning uniformly and the barrel is moving slowly in the cycle then small change in the velocity will not cause a large variation in point of impact. As for seating depth, it has a very small effect on the POI but due to the behavior of the bullet and its orientation in the rifling will affect the dispersion around the POI.

Because the bullet velocity primarily affect the POI variation and the seating depth primarily affects the precision/shot dispersion it is entirely possible to do the load development starting with either seating depth or powder charge.

 

[COLT45SA]

I don't understand.... In order to adjust seating depth, don't you have to have a "pretty close" charge weight? How do you determine what charge to start with before you start with seating depth? I feel like a dog chasing my tail sometimes...

My thought is that you have to try both charge and seating depth. I personally would start with powder charge. Once I found a node in charge weight I'd go to seating depth. Once I had found the best of both I'd go back to tiny charge weight increments.

 

[ELR LVR]

I’m a start with powder guy but I have a good idea where the bullet likes to be, so am I really starting with powder first ?
On the other hand guys that start with seating depth test first have an idea where the powder charge should be, so are they really starting with seating first ?

Jim

This is actually,
a very excellent point!
I normally know where to begin with powder charge for the desired velocity
I will run a quick ladder until I find pressure signs then back off
A quick ladder may only take 5-10 rounds
Then Focus on Seating depth until all shots start going into a small group consistently
Then go back and tweak powder charge from there to dial it in.
---------------------
It's really a balance of tuning both things
But without the proper seating depth, I could not then go back and fine tune the powder charge
--------------------
However!
Once I find the seating depth the rifle likes
If I switch to a different powder, I already have my seating depth so then all further tuning is with powder charge only

 

[JFrank]

will run a quick ladder until I find pressure signs then back off

With nodes mostly repeating approx 3% apart , anti nodes seem to as well, so not only am I looking to identify a decent node to work seating depths I’m also looking to stay away from the more unstable anti node. On the target below I’m in a stable spot at 31.2 - 31.6 but 31.7 through 32.0 is kinda no man’s land so I don’t think I would trust any seating data from that charge rate.
Question;
So if we just find pressure ( at 32.4 ) how far would you back of to start your seating depth testing ?

Jim

 

[ELR LVR]

With nodes mostly repeating approx 3% apart , anti nodes seem to as well, so not only am I looking to identify a decent node to work seating depths I’m also looking to stay away from the more unstable anti node. On the target below I’m in a stable spot at 31. 4 - 31.6 but 31.7 through 32.0 is kinda no man’s land so I don’t think I would trust any seating data from that charge rate.
Question;
So if we just find pressure ( at 32.4 ) how far would you back of to start your seating depth testing ?

Jim

Much like what you're saying here
Within the ladder (Say 10 shots)
I look for stable AND note erratic behavior in the shot placement
As well as velocity
For instance I remember working a ladder going from 49.0 grns up to 52.0 grns
at 51.0 shot placement was Spot on, exact
at 51.5 Velocity did not increase much, maybe 12 fps
So I held at 51.0 grns because POI to POA was more consistent and proceeded to keep testing at 51.0 for consistency.
----------------
That's the load I used to shoot the pictured group (And many others like it, this is just the first time the load confirmed its consistency )
first it was a 3 shot
then came back later and reset up
and put another round right into the same group pictured
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I notice some guys here are saying they also look for POI relative to POA withing their load development
I know sometimes when going up the ladder shots may start printing right or up etc.
and guys like me say - Just re adjust your scope
But I think what they're saying is what I am doing without thinking it....
I want to see.....................that my shots keep producing the same
POA=POI ( during the ladder even though we CAN adjust the scope to compensate if it migrates out)
I don't adjust the scope yet because I want to see how far away from POA the shots migrate as I work up the ladder.
So when all shots POA =POI
Whether I setup here or down the road or at another range etc.
if the shots seem to naturally go to POA
Almost without trying, as if the bullet hones in on your POA,
.... I migrate to the charge that produces those results
even if it is 12 fps slower lol or (even if it is 50 fps slower)
------------------
Good point on the Anti-Nodes
because some of us may want more velocity and simply adding more powder isn't the right way if we bring the load into an Anti-node
So how far would I back off once reaching pressure you asked?
I would back off to the last charge weight that was putting rounds into consistent POA's
Or where POA equaled the most consistent POI's
------------------
Another quick and dirty way to run a ladder I have done is
Shoot a 10 shot group at one POA
This would be similar to the waterline test, except you're keeping the same POA instead of each shot being a new POA.
Watch where all those shots go
1st and 2nd may be 1/4" away and then there will be 3 or 4 shots you will see going right into the same hole
then the rest will start to migrate out again.
Now work the load with those 3 or 4 shots that went into the same hole and fine hone the load
this is just if I am trying to get a buddy's or my gun to shoot within 1/2" real quick maybe for a hunt or varmint shoot or something, its quick and easy

I've developed a lot of loads for other people and got tired of having to shoot 100 rounds or more or repeated trips to the range as if Im developing a benchrest load, when it wasn't really necessary.
So this method could also be used to find a good starting point to fine tune any load really.

 

[ELR LVR]

This is an example of a seating depth ladder test keeping the same POA
Different seating depths, but noting where each shot goes
When they cluster tighter together is where I like them
When I see them start to cluster, and hold then spread back out
in the middle of that is my tune window
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I like this better than the waterline sometimes because
using the waterline test means you have to move your POA setup for each successive shot
instead of remaining at the same comfortable POA rest you just developed
I shoot prone so this is important for me
I practice how I normally will be shooting in real life
so it makes no sense for me to shoot off a bench if I am actually going to be shooting prone out in the field

 

[Wild Bill IV]

I'm very impressed with the knowledge and experiences of this thread!!!!!!
Especially ELR LVR and JFrank!!!! I use to think charting the velocity was the fastest and easiest way to tuning! Boy, was I wrong! The internet is full of short cuts to tuning, and should be taken with a grain of salt!!! But, this website has totally changed the way we use to work up loads long ago!!!

JFrank nailed it!!!! In my studies of harmonics and waveforms, there are indeed constructive nodes (the tuned loads) and destructive nodes (anti nodes) on harmonics!!!! These two types of nodes generally alternate within one full cycle of the wave! The harmonics of the barrel is just like a diving board, but the steel barrel doesn't react near as much as the fiberglass board!!! Trying to tune up an anti node is a waste of time and materials!!! And ELR LVR stated you need to get POI almost equal to POA! That is the constructive node or tuning load!!
If you can't get close to POI = POA, move to the next node!!!! And like he stated, find the load near just below the high pressure sign(s)!!! After all, the reloader needs to know that critical point of the high pressure signs!!!

I'm neither a BR or LR competitor, but a LR hunter using both BR and LR theories and implemented practices!!!!!!

Thank you JFrank and ELR LVR for sharing!!!!!

 

[Bc'z]

With nodes mostly repeating approx 3% apart , anti nodes seem to as well, so not only am I looking to identify a decent node to work seating depths I’m also looking to stay away from the more unstable anti node. On the target below I’m in a stable spot at 31.2 - 31.6 but 31.7 through 32.0 is kinda no man’s land so I don’t think I would trust any seating data from that charge rate.
Question;
So if we just find pressure ( at 32.4 ) how far would you back of to start your seating depth testing ?

Jim

1-1.5gr is about where I start after collecting information on max charges for a given cartridge.
And by the looks of your ladder that's where it's happy place is.
So theoretically if you had started at 31gr with a seating depth test, you might've gotten there quicker.

 

[JFrank]

1-1.5gr is about where I start after collecting information on max charges for a given cartridge.
And by the looks of your ladder that's where it's happy place is.
So theoretically if you had started at 31gr with a seating depth test, you might've gotten there quicker.

Yeah I would say 31. would have been safe but I didn’t know that at the time.
I’d have to look at my notes to be sure but I want to say I stayed around 31.4 or 31.5 and tested seating.
I remember it was about 10 * that morning and dead calm, my 500 yard target was pretty clear.

 

[Gil P.]

6.5x47 lapua, 139 scenars, NV N555, cci ar primers, setting depth 20 thou off lands, test was done when it was about 100 degrees outside...

I start with testing powder charger first. This was a ladder test down at... I think 500 yards? My memory is a little fuzzy on the distance. Its an old picture.

I settled on 40.1 grains. The average velocity varied 7 fps from 100 degrees to 40 degrees. Excellent accuracy in different conditions.

I test my powder first, then go back and adjust seating depth. In this case I just left the seating depth alone.

 

[ebb]

^^^^ anything that would convince me I had found a load would contain many targets.

 

[jelenko]

^^^^ anything that would convince me I had found a load would contain many targets.

Yeah. I had no idea what those shot were supposed to represent.