600 Yard Ladder Results

[MattPeetz]

The difference between 4-7 is 3. Divide by 2, is 1.5.
Add 1.5gr to the number 4 charge. Use that charge and do your seating ladder.

 

[APGE]

Whether you're using a ladder test, or OCW (or some similar variant thereof), it is best to conduct the tests using methods that have been proven to work. For example, you can do a ladder test at a much closer distance than 600 yd. The advantage in doing so is to minimize shot dispersion due to wind, which may not solely be in the horizontal dimension. However, when you do this you're also shrinking the y-axis (vertical dispersion), which may make it more difficult to decipher the charge weight/node information from the target correctly. From your target, it appears as though the wind was not a huge factor. As has been noted, using a ladder test at the distance you intend to shoot also has the benefit of allowing you to directly interpret vertical dispersion as it relates to charge weight, without any distance-based assumptions. If you shoot in a place where the average wind conditions are typically very strong/challenging, the issue of added dispersion due to the wind can make interpretation of your targets more difficult at longer ranges.

Similarly, shooting 3- or 5-shot groups in OCW fashion at 100 to 200 yd will generally provide you with similar information, although you're looking for movement of of the center point of a group around your point of aim with respect to varying charge weight as opposed to vertical spacing of individual impacts as in a ladder test. The advantages of this approach is that wind dispersion will typically be less of a factor, as well as the fact that not everyone has ready access to ranges that extend beyond 300 yd or so.

The bottom line is that there is really no good reason to mix the two approaches. Each has its strengths and weaknesses, and each can provide similar information if carried out correctly. Unless the day you shot your target was the only mild wind day you'll experience in the near future, I'd strongly suggest repeating your ladder test exactly the same way you did it the first time, focusing on charge weights #3 to #8. In reality, #4 to #7 clearly look like your node, but you can't define the boundaries of the node if you don't also include charge weights that are outside it. One repeat with those charge weights is very likely all you'll need. At that point you can load to the center of the charge weight node and move on to seating depth testing by whichever approach you prefer. The main point is that your first ladder test appears to have worked very well. Why switch to a different approach merely to confirm what the ladder test has already suggested?

Thanks for the detailed reply, Ned

I was lucky enough yesterday that I had very still conditions, so as you've observed, wind was not a factor.

I was going to shoot a second ladder yesterday but ran out of daylight, so I already have rounds loaded to repeat the test - I may as well go shoot 3-8 again as you've suggested rather than pull the bullets.

An interesting observation -
I usually use quickload and OBT to develop a load, shooting groups either side of the prediction at 200 yards. In the past it has worked exceptionally well as a starting point, but I abandoned it after some abysmal results on the last rifle I was working up a load for and went straight to the ladder for this one.

After plugging in all the relevant data to quickload for the target I shot yesterday, it tells me there should be and OBT node just shy of charge number 5. It's nice when things work out like that.

 

[MattPeetz]

Hmmm. Go figure. Don’t need a computer program to tell me where the node is. Smiley face!!

 

[JFrank]

A lot of good information here,
I would like to follow your results,
Please report back.
J

 

[Ned Ludd]

Thanks for the detailed reply, Ned

I was lucky enough yesterday that I had very still conditions, so as you've observed, wind was not a factor.

I was going to shoot a second ladder yesterday but ran out of daylight, so I already have rounds loaded to repeat the test - I may as well go shoot 3-8 again as you've suggested rather than pull the bullets.

An interesting observation -
I usually use quickload and OBT to develop a load, shooting groups either side of the prediction at 200 yards. In the past it has worked exceptionally well as a starting point, but I abandoned it after some abysmal results on the last rifle I was working up a load for and went straight to the ladder for this one.

After plugging in all the relevant data to quickload for the target I shot yesterday, it tells me there should be and OBT node just shy of charge number 5. It's nice when things work out like that.

I've had a number of loads that ended spot on predicted OBT nodes. Too many to believe it's mere coincidence, even if I am not satisfied with the proposed mechanism by which it is supposed to work. The problem with OBT nodes is that there are many combinations of bullet weight and barrel length for which it is impossible to hit the desired barrel time at safe operating pressure. Fortunately, the 225s and H4350 with your setup don't seem to be one of those combinations. It's looking good so far, keep at it!

Just out of curiosity, what % case fill ratio values does QuickLoad give you for charge #5 (44.0 gr) and charge #9? It also appears that you may have another node at #8/9/10, although it doesn't look as good as the lower node. QuickLoad may sometimes permit you to rule one out if the fill ratio at one node or the other is well under about 93-95%, or over about 103-105%. If you have good velocity data, predicted pressure is also another way to help decide whether an apparent [high] node is really worth pursuing further.

 

[APGE]

OK gents - round number 2!

Not exactly the results I was expecting. I shot loads 3-8 from yesterday's ladder and between 4 and 7 I went in 0.1gr increments The numbers in brackets represent the corresponding load number from yesterday

Today's conditions were not as favourable as yesterday's with a mild gusting wind. I am time poor when it comes to shooting, so I elected to shoot the ladder and do my best to pick still conditions. I am confident wind took shots 43.7 and 43.9 wide and possibly high. There's 2.2" of vertical between 43.7 and 44.1 and the ladder was shot from 600 yards. This node would be about 0.4gr wide.

44.6gr destroys what might have been a good node at the top.

So accurate shooter forum - load up number 43.9 and start playing with seating? If the horizontal in shots 43.7.and 44.1 was not wind induced, I should be able to dial that out with my tuner, I would expect.

I'm a little flummoxed - load 43.9 is more in line with the results of the first ladder, so my inclination is to use it, but I'd appreciate the input of those more experienced than I. I would also like to know if a half grain wide node is what I should expect to see in a 308 using 44ish grains of powder.

Thanks again, all the advice is much appreciated.

 

[Ned Ludd]

This target is a little more complicated. It would be helpful if you could simply put the corresponding charge weight next to the appropriate bullet hole. If I understand the notation correctly, it still looks like you may have something worth pursuing on the new target around charge weight #5 (same nomenclature both days?) and a higher node around charge weight #9 (day #2 nomenclature, between #6 and #7 from previous target?). Although I don't shoot bullets that heavy in a .308 Win case with H4350, in my hands, I've never seen a node with a .308 load that was 3 or 4 x 0.3 gr increments wide. Not saying it isn't possible, but that would be a really wide window for a .308 case. That made me wonder a bit about your previous results, where 4, 5, 6, and 7, were all closely grouped vertically. To be honest, it doesn't necessarily matter. This target suggests that testing in a finer charge weight increment than 0.3 gr around #5 and possibly #9 will still get you where you want to be. Yes, it means more charge weight testing. However, a ladder test that can be reproduced is one that gives you confidence you have selected the appropriate charge weight to work with further. Stick with it.

 

[APGE]

I've had a number of loads that ended spot on predicted OBT nodes. Too many to believe it's mere coincidence, even if I am not satisfied with the proposed mechanism by which it is supposed to work. The problem with OBT nodes is that there are many combinations of bullet weight and barrel length for which it is impossible to hit the desired barrel time at safe operating pressure. Fortunately, the 225s and H4350 with your setup don't seem to be one of those combinations. It's looking good so far, keep at it!

Just out of curiosity, what % case fill ratio values does QuickLoad give you for charge #5 (44.0 gr) and charge #9? It also appears that you may have another node at #8/9/10, although it doesn't look as good as the lower node. QuickLoad may sometimes permit you to rule one out if the fill ratio at one node or the other is well under about 93-95%, or over about 103-105%. If you have good velocity data, predicted pressure is also another way to help decide whether an apparent [high] node is really worth pursuing further.

I've had several that have ended up exactly on QL OBT nodes too. I've also had several people call BS on that claim, but it works.

I'm at 101% at load number 5 and 103.8% at load 9. As much as I would like to explore a higher node around 8-10, the case head expansion I measured on the cases from 9 upwards, was significant. I haven't reloaded them yet but I'm suspicious about their future capability to hold a primer! Maybe with palma brass, but even then the action on this rifle is only a blueprinted remington, so I'm not sure I want to push the envelope.

I really need to get the chronograph out and get a bit more serious, but I'm scratching for time to get this sorted as it is

 

[Ned Ludd]

It sounds very much like your charge weight #5 is where you want to be. It's giving you positive feedback in a ladder test, it corresponds to an OBT node via QuickLoad, it's right where you want to be in terms of case fill ratio, and it sounds as though you're still below acceptable max pressure. From what you just stated, if you decide to do further charge weight testing, I'd focus solely on #2, 3, 4, 5, 6, corresponding to your lower grouping on the most recent target. If you feel like you have to move on for time reasons, do a seating depth test with #5, then take the end result and shoot groups at 600 yd over the chrono to to validate that it is holding up. Good luck with it!

 

[APGE]

It sounds very much like your charge weight #5 is where you want to be. It's giving you positive feedback in a ladder test, it corresponds to an OBT node via QuickLoad, it's right where you want to be in terms of case fill ratio, and it sounds as though you're still below acceptable max pressure. From what you just stated, if you decide to do further charge weight testing, I'd focus solely on #2, 3, 4, 5, 6, corresponding to your lower grouping on the most recent target. If you feel like you have to move on for time reasons, do a seating depth test with #5, then take the end result and shoot groups at 600 yd over the chrono to to validate that it is holding up. Good luck with it!

Ned,

Thank you so much for your input - it's been very valuable. I updated my last post with a plot of today's ladder with the corresponding charges next to them. I also put yesterday's numbers in brackets next to them. I think you worked out my scribble on the other target anyway, but the updated post should clarify things.

Charge 5 seating depths then chrono sounds like the logical next step

Thanks again.

 

[seymour fish]

OK gents - round number 2!

Not exactly the results I was expecting. I shot loads 3-8 from yesterday's ladder and between 4 and 7 I went in 0.1gr increments The numbers in brackets represent the corresponding load number from yesterday

Today's conditions were not as favourable as yesterday's with a mild gusting wind. I am time poor when it comes to shooting, so I elected to shoot the ladder and do my best to pick still conditions. I am confident wind took shots 43.7 and 43.9 wide and possibly high. There's 2.2" of vertical between 43.7 and 44.1 and the ladder was shot from 600 yards. This node would be about 0.4gr wide.

44.6gr destroys what might have been a good node at the top.

So accurate shooter forum - load up number 43.9 and start playing with seating? If the horizontal in shots 43.7.and 44.1 was not wind induced, I should be able to dial that out with my tuner, I would expect.

I'm a little flummoxed - load 43.9 is more in line with the results of the first ladder, so my inclination is to use it, but I'd appreciate the input of those more experienced than I. I would also like to know if a half grain wide node is what I should expect to see in a 308 using 44ish grains of powder.

Thanks again, all the advice is much appreciated.

Did you shoot with flags? Any chance being short of time , you rushed your setup or delivery ? What was direction of wind gusts ? Any chance there was some vertical-inducing turbulence, headwind or tailwind affecting vertical placement ? You should find the meat of the node to be min 0.4 grs wide, and would prefer 0.6. Consider switching powder if you do not quickly achieve that. Consider this second Ladder was blown ? Seating test: 3 shots each incremental change. Starting pressure will be significantly lower, so further powder titration afterward, in tenths, 3 shots each, and you’re done. Once load optimized and chrono Ed, backfeed into Quickload. Adjust to match proven MV. Bet you come in at 1% longer than OBT as an aside

 

[Bart B.]

Note that a given wind only in the first third of target range causes over twice the drift at the target than the same wind only in the last third.



How much better will the first ladder test results be with 2 or 3 shots per load instead of 1?

 

[dsculley]

Maybe it is just me, but I think 44.3, 44.4 & 44.5 looks very promising. Those are 1/2" squares? That would mean about 1" vertical in this group. I would load 10 rounds of 44.4 and see how it performs. If the results look good but need some tweaking then i would perform the Berger seating depth test to see if it would tighten up.

Just my 2 cents.

 

[Ned Ludd]

Maybe it is just me, but I think 44.3, 44.4 & 44.5 looks very promising. Those are 1/2" squares? That would mean about 1" vertical in this group. I would load 10 rounds of 44.4 and see how it performs. If the results look good but need some tweaking then i would perform the Berger seating depth test to see if it would tighten up.

Just my 2 cents.

He already mentioned that those charge weights are killing the brass. Likely too hot.

 

[APGE]

He already mentioned that those charge weights are killing the brass. Likely too hot.

That, and the window there is only 0.2 gr wide. I'd loose my tune depending on the time of day I was shooting with something that narrow

 

[JFrank]

OK gents - round number 2!

Not exactly the results I was expecting. I shot loads 3-8 from yesterday's ladder and between 4 and 7 I went in 0.1gr increments The numbers in brackets represent the corresponding load number from yesterday

Today's conditions were not as favourable as yesterday's with a mild gusting wind. I am time poor when it comes to shooting, so I elected to shoot the ladder and do my best to pick still conditions. I am confident wind took shots 43.7 and 43.9 wide and possibly high. There's 2.2" of vertical between 43.7 and 44.1 and the ladder was shot from 600 yards. This node would be about 0.4gr wide.

44.6gr destroys what might have been a good node at the top.

So accurate shooter forum - load up number 43.9 and start playing with seating? If the horizontal in shots 43.7.and 44.1 was not wind induced, I should be able to dial that out with my tuner, I would expect.

I'm a little flummoxed - load 43.9 is more in line with the results of the first ladder, so my inclination is to use it, but I'd appreciate the input of those more experienced than I. I would also like to know if a half grain wide node is what I should expect to see in a 308 using 44ish grains of powder.

Thanks again, all the advice is much appreciated.

I always struggle with long range ladders, BUT if it were me I would start seating at 44.gr

 

[Bart B.]

Horizontal dispersion is also caused by barrel harmonics not unlike vertical. Giving some the wrong impression that wind is the only force to blame for the shots going to the left or right.

Tuners adjust the muzzle line of fire (bullet departure axis) vertically positively compensating for muzzle velocity spread.

What do they do to the line of fire, horizontally, that makes bullets go left or right?

I ask because I've never thought there was enough angular spread horizontally in line of fire to be a concern.

 

[normmatzen]

I believe that 1-3 shot ladders don't have the statistical accuracy you need to get this data.
Consider the inherent accuracy of your gun.
If you are testing a hunting rifle, you have a gun that is 1-2 MOA accuracy so comparing two isolated shots means they could be 6" to 12" apart at 600 yds. If you had a gun like a PRS you have maybe 0.5-1 MOA for a spread at 600yd of 3" to 6". If you have a properly built Bench Rest gun you may have 0.25MOA for 1.5" spread. For good accuracy you should be shooting 5 shot groups at minimum.
I characterize my BR barrels with round robin 5 shot groups at different loads (1% steps) and analyse the Mv to find ES of each load. Then evaluate these data with an EXCEL curve fitting process to find exact best load. Now, I have the tightest Mv this gun is capable of. Then I tune my tuner at range, usually 1000 yd.
The first tune for ES accounts for longitudinal resonance (Like an organ pipe) then, the tuner tuning at distance tunes for cantilever or vertical resonance (like a bridge wiggling up and down).

Doing a ladder test at distance will combine both tests but one must keep the data statistically accurate so 5 shot groups minimum per load.

 

[seymour fish]

First time I’ve heard the notion of ES/longitudinal resonance correspondence. Food for thought. Correlation with OBT predictions ?

 

[normmatzen]

Mr Fish,
Check out Varmint Al's web site as well as a book
by Graham Mincham called Optimum Barrel Length. You may not want to do what Mr. Mincham prescribes as it entails shortening the barrel a bit. I and my Australian friend do the longitudinal tune then tune our tuners. This book is sold by South Australian Rifle Association
phone # 0882445533.
Varmint Al has some great articles using Finite Element Analysis about rifle resonances. He also connects it to the OBT theory.