Help interpreting 1st ladder test data.

[srawl]

hello,

So my old method was load 10 of a few suggested loads (not going over max) and keep the best. That worked well enough but I wanted to try something to conserve a bit of ammo and maybe even get better accuracy.

Here are my results from 4 ladders at 200 yards. They were transferred from the original targets for ease of interpretation.

This is my first attempt at this and the weather was pretty bad. Rainy and windy. I can pretty consistently shoot moa or under but I do make mistakes.

I've wrote on them where I see a node and the vertical distance but please feel free to share your knowledge. One thing I've noticed is most of the nodes are on the lower end. I don't have a chrono but want loads that are still good at 3-500.

All were shot with 8208xbr

1: 50 gr vmax
2: 55 gr vmax
3: 68 gr hornady match
4: 69 gr Sierra matchking

Thanks for your time

 

[Load Master]

What are you shooting? Barrel length and twist rate? How are you shooting? Standing, bench, floor?

 

[srawl]

16" Ar15 Rainier ultramatch 1-8" twist 223 wylde off bags on a bench.

 

[Load Master]

I can't offer much in the way of interpretation as I don't fully understand your process. However, with .223 Rem the atmospheric conditions you mentioned could be a big factor in the results.

On a side note, the V-Max 50gr produces my tightest groups. I use IMR4198 and H-335. My barrel is a 18 inch Wylde also 1-8 twist.

 

[Joshboyfutre]

I think with the ladder test that you are using your not only looking for vertical spread, but also horizontal spread. Looking at the targets it does look like there are a few groups that are reasonably tight.
Tgt-1: 8,9,10
Tgt-2: 3,4,5
Tgt-3: 1,2,3,4
Tgt-4: 3,4,5
That being said I've never actually used this method, just read about it. I do specifically remember it saying you want sequential loads that are as close to the same spot as possible. Basically trying to pinpoint when the barrel is most stable with that load. If it were me I would go out and do a small load test with 6 to 9 of each of the loads I mentioned and see how they perform. Alot if shooting tho, might just do one and see how it turns out. Like I said tho, Ive only read about this method never used it myself.

 

[redbullitt]

I would not worry much about your horizontal spread. That can be wind for sure with the 223, and it does not really tell you a lot about the barrel's preferred "nodes." The only rub there can be if the barrel is not straight, mind you just a little goes a long way with that lol. Probably not an issue on a good barrel at all.

You want the load that offers minimal vertical dispersion, provided you are shooting well. At that point you should be near the loading that has the bullet exit the barrel at the very top or bottom of the barrel vibration/wave movement. You will probably also be able to find the loading that offers a good consistent FPS at the same time. Find that and you have a good starting point to start making small adjustments in seating depth and charge weight. I would make sure conditions are favorable and youre shooting cleanly, otherwise you can wind up chasing your tail a bit.

Generally the ladder test will work better at a longer range, say 350 or 400, but your testing will show it as well. Greater distance will make the favorable loadings stand out a little more and be easier to pick out from the others.

 

[Bart B.]

Basically trying to pinpoint when the barrel is most stable with that load.

There's two places where the last few inches of the barrel controlling the line of fire axis is stable; at the very top and very bottom of its angular range. If at the top, slower bullets will leave while the bore axis is on the down swing, faster ones on the upswing. If at the bottom, it's the opposite.

Wouldn't it be better if all bullets left on the bore axis up swing to compensate for all bullets' velocity spread?

http://www.varmintal.com/alite.htm

 

[bikemutt]

There's two places where the last few inches of the barrel controlling the line of fire axis is stable; at the very top and very bottom of its angular range. If at the top, slower bullets will leave while the bore axis is on the down swing, faster ones on the upswing. If at the bottom, it's the opposite.

Wouldn't it be better if all bullets left on the bore axis up swing to compensate for all bullets' velocity spread?

http://www.varmintal.com/alite.htm

Not trying to be smart; does a barrel always have an up/down motion, or is a left/right motion possible?

 

[Bart B.]

First off my bat; I like people like you to ask questions; something all smart people do.

Yes, some amount of up and down motion happens. That's because the center of mass of the rifle is below the bore/recoil axis. It's modified some by where the center of mass is of the human holding the rifle relative to that same recoil force the butt stock transfers to the human. There's horizontal motion, too, because the mass of the human is centered off to one side of the recoil axis.

Then the natural whipping and wiggling of the barrel from forces of the cartridge firing. Here's a site that uses computer modeling of metals often parat of mechanical engineeing work with vibrating structures; earth quake's effects on buildings and bridges.

http://www.varmintal.com/amode.htm

Here's one you can profile your own 30 caliber barrel and offset the rifle's center of mass to see how a free recoiling rifle barrel wiggles before the bullet exits, then using a 1.2 millisecond barrel time for the 308 Win cartridge this example is based on, see the angle the muzzle points when the bullet leaves compared to when the barrel was still:

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/barrel_vibrations.htm

After one grasps the significance of all this stuff, they should realize how important it is to have a totally free floating barrel so no external pressures from anything will alter the barrel's otherwise very repeatable vibration characteristics.

Some people put tuner weights on the muzzle end then adjust it back and forth until bullets stop vertical stringing down range then have none at all. They're changing the barrel's frequencies it wiggles vertically so slower bullets leave on the bore axis up swing before slower ones do. That compensates for the slower bullets greater drop down range. It's called positive compensation.

 

[noylj]

target 1: 2, 3, 4 have the smallest vertical dispersion
target 2: 3, 4, 5 have the smallest vertical dispersion
target 3: 1, 2, 3, 4 is one group and 5, 6, 7 is the next group.
So, load some around #3 in target 1, around 3 and 4 in target 2, and around 2 and 3 and then around 6 in target 3. Looks like the 1,2,3,4 might be better than 5,6,7 for ultimate group size, but more shooting will tell the tale.

 

[Bart B.]

Did you use incremental powder charge weights for each shot? If so, how much?

I'm always skeptical of ladder tests. I've never seen one repeated several times to see if they all produce the same results, It's shooting a "group" of the same ladder test. I doubt they'll be very repeatable. 3-shot groups with the same load can have a 4X spread from smallest to largest; the first one is not always the smallest.

What's the probability of each one shooting each charge weight's bullet to the same place?

Wouldn't each charge weight have to shoot its bullet very accurate to get the same results each time?