Ladder Test suggestions???

[xdeano]

Well Here is a target that I shot this morning @300yds with a 308 using 155g Lapua's, and Varget ranging from 42.8 to 46.6g.
I'm having a heck of a time figuring out which load to pick for a load test. The target is on an 8.5x11' piece of paper with a 1'x1' square. Aim point is the square. I'm just looking for you guys insight.

1 2672 fps
2 2691 fps
3 2714 fps
4 2711 fps
5 2740 fps
6 2746 fps
7 2747 fps
8 2772 fps
9 2778 fps
10 2785 fps
11 2784 fps
12 2821 fps
13 2796 fps
14 2822 fps
15 2837 fps
16 2860 fps
17 2867 fps
18 2873 fps
19 2871 fps
20 2869 fps

I tried this same load string at 200yds and all i ended up with is a ball of shots the size of a golf ball. There was no vertical stringing like I was looking for. I could also go a bit further on the powder because I wasn't snowing any huge pressure signs. It was really funny why 16 -20 opened up huge and high.
I thought I'd pulled the shot, but I knew I hadn't.

Any help would be greatly appreciated guys.

xdeano

I'm leaning toward shot 3,4,5,6 it comes out as 1.252' center to center. I'd like to find a load with a higher velocity though. But i'll take what I can get. Or would you redo the test?

 

[scout1]

xdeano,

shots 1,2,3, look pretty good as far as horizontal plane. 4,5,6 arent that far off either. Did you shoot any fowlers to warm the barrel before you started your ladder?

Were you shooting over wind flags at 300? You might be surprized how much a little breeze you didnt notice can move your impact.

 

[xdeano]

I wasn't shooting with flags, There was a 6mph wind at my 10 oclock, but i had a shelter belt that was blocking the wind. I though it might have a little affect. I also didn't bring a spotting scope and I couldn't see my holes, so I had to run down there on the 4 wheeler every time. It sucked.

I didn't shoot any fowlers, so my barrel was basically a cold bore everytime.

xdeano

 

[jb1000br]

12/13/14/15

Time between shots?

Definitely try higher if you can. Once you find your max, shoot it in reverse order to see if the clustering repeats.

Don't bother at 200...

Don't sweat windflags,with a ladder test) and only measure vertical.

JB

 

[TonyR]

Deano, There are lots of ways to do it but I like to use a slight variation on Jason Baney's method. Jason's method is on this site: http://www.6mmbr.com/gunweek070.html and http://www.6mmbr.com/laddertest.html
He color codes his bullets and shoots at one bull. I use a separate point of aim for each powder charge. I only hold for and measure vertical and use a target with a grid and an orange cross with points on the ends which helps keep the hold consistent, both elevation and the leveling of the gun. I first shoot groups of three shots for each powder charge I am testing and repeat the process three times for each powder charge but change the order in which I shoot them. Jason includes cooling periods between groups and warm up shoots after the gun has cooled off. I shoot F-Class and shoot 22 rounds in about 10 minutes in competitions so I actually want the find loads that work well without time for the gun to cool off except at the end of each of the three series. Anyway, what I look at is the vertical distance of the center of the group from the point of aim and the vertical dispersion within each group. As the charge goes up, the center of the group will go up until I am in the node then the center of the higher charges will actually roll over and impact lower than lower charges. I use 0.2 grain increments with the 6mmBR and 0.3 with the 284 but some people do fine with 0.5 with the bigger cases. With my guns, the vertical dispersion usually reaches a minimum in the vicinity of the roll over unless the seating depth is way off. Then I will repeat the process with groups of 5 shots of the three charges around the node again repeated three times in different order. Then I pick the best of those and repeat the process with different seating depths. This eats up a lot of ammunition but it does work consistently and I believe it is necessary to shoot 40-50 rounds before you have enough data for a valid analysis at each stage of the process.
Looking at your target, I would note that 16 is the highest and 19 and 20 look like they have rolled over so, I would be very interested in shooting some more of whatever charges are on both side of that point. It also looks like 12, 13, 14 and 15 are doing the same thing with less vertical even though the velocities trend up. So that would be another charge range to explore.

 

[ThunderDownUnder]

I dont shoot 308W but I noticed your velocity might be a little on the low side. Most of the shooters with the 155gr bullets are in the 2900-3000fps range of velocity.

I guess it depends on how your rifle handles pressure, length of barrel, etc, but if you can, then increase the velocity. Bryan Litz in his new book on ballistics says that around 3000fps is popular in Palma shooting 155gr projectiles. It would be worth a try going into the mid 2900fps just to see if it makes big difference for you.

 

[TonyR]

Deano, Is this your 22 inch barrel and were 12, 13, 14, and 15 about 46.0gr of powder??

 

[xdeano]

TonyR,
Yep this is that 22' Bartlein, I was using my velocities on the other post of my 26' barrel if that's where you're going.

.2 grain increments.
#12 45.0g
#13 45.2g
#14 45.4g
#15 45.6g
....etc.

I thought that I'd have more pressure signs than I had at 46.6g, my other rifle was flattening and had pretty bad primer flow.
I'll take a look at those links Tony, thanks. I shoot Fclass also but I also shoot for work and am usually out during twilight hours when it's cool.
My temp changed from 56 - 60 degrees F this morning while I was shooting.

Thunderdownunder,
I would love to get my bullets in the 2900-2950fps if at all possible without blowing myself up. They seem to run better in the 2900fps range for some reason.

jb1000br,
time between shots was about 2 minutes i'm guessing.

thanks guys.

Deano

 

[xdeano]

Tony,
I read through the first thread then I started to think about what you had said about 16-20 having rolled over. Then I reread your post about being interested in seeing whats on both sides of that point. Which point were you referring to? Shot 19/20?

I'm fairly new to the Ladder test, so bare with me. I'm a bit slow. All I've ever done before is group tests in a round robin type setup.

I think what i'll do the next test is have a buddy come out to the range with me and I'll shoot from the berm and have him pull two targets for me and i'll go from high to low at 300.

Thanks
Deano

 

[TonyR]

Deano. 19 and 20 do roll over but with a lot more vertical than those down in the 12, 13, 14 vicinity. First of all, I am also surprised that you didn't see more pressure signs at 46.6gr because QL says that that load is over max pressure and porbably 8-9% compressed if I have your seating depth close. I used an overall cartridge length of 2.850 inches. 45.2gr shows about 5% compressed and below max pressure. Now look at the vertical sequence of 10, 11, 12, 13, 14, and 15. Notice how they progress down vertically from 10 to a nice tight pair at 12 and 13 and then 14, and 15 start rising on the target and 16 is way up high. I suspect that there is a sweet spot close to 45.2gr. To test that, I recommend that you shoot three shots each at 44.8, 45.0, 45.2, 45.4, and 45.6gr and see what happens. If you have the time, you might do those three times each in a different order. It is hard to tell much from a single shot at each powder charge and the 308 Win usually has great barrel life.

 

[xdeano]

Tony,

I really appreciate the excellent direction that you are giving me. I'll give those loads a work over and post my findings. I just have to wait for a good morning with low wind.

You're right I am crushing powder at around the 13 or 14 round mark. That'll put me right in that 2800fps mark and I'd be ok with that. I wouldn't mind a bit more, but with a 22' barrel I'd be happy with that. Less powder means more bullets down range, can't go wrong.

Thanks again,
Deano

 

[TonyR]

I would appreciate seeing your test results. I still have to develop loads for my friend's 308 Win Ruger 77 with a 22 inch barrel. We are going to try Varget, IMR-3031, and perhaps BL-C2 and N540 for that with the 165gr GameKings.

 

[xdeano]

I'd like to try N540 but it's so dang hard for me to find VV powder up here in the ND. I have some 3031 that I should try but i'm more worried about temp sensitivity as well, as you probably already know. If I find a place that carries the N540 I'm going to snap up a few pounds of it just to play with.

I'll keep you posted. Thanks again.

Deano

 

[TonyR]

There are some many possibilities, it gets confusing. I am familiar with most of these powders from my 6mmBR. I ended up using N540 because it gave me enough extra velocity with my 31 inch barrel to get to a node higher than the Varget gave me, but the extra velocity would mean nothing if it left me short of the next node. My best vertical with the two powders was the same so I took the higher velocity node with the N540 and refined that. Since you want to shoot this gun at 1000 yards, that extra velocity would be nice but not at the expense of vertical precision. I think it makes sense to first find the Varget node and then perhaps try to see if the 3031, which you have, gives you enough extra velocity to get to the next node.
Good luck.

 

[normmatzen]

I would try 3-5 shots per load and make the graduations larger at first, then smaller.

I,too, use the ladder, but after primary results, I still fall back to 4 or 5 small targets next to each other and shoot 5 shot groups at each with each shot at a different target so that one target isn't done at a different part of the heat cycle of the barrel..Or, load 1 target 1, load 2 target 2, load 3 target 3 then back to load 1 target 2 and so forth.

Then, you can compare groups to find the tightest,,

The ladder is still a powerful tool, but I have never tried one shot per load as there is no way to integrate shooter errors with only one shot. With 5 shot groups, one flyer can be ignored. With one shot per load, a couple flyers confuse the issue too much.
Bear in mind, I'm a new comer to this game, so take my advice with a grain of salt!

 

[KentuckyFisherman]

Gotta concur with Tony, I spotted the very same cluster that he did. When I run a ladder, I try really, really hard to focus on the vertical and,generally) ignore the windage spread. If you look at shots 12-15 they are very tight vertically. If you look at the velocities, there's very little spread between shot #12 and #15. In addition to tight vertical groups, I look for a flattening of velocity at a node, sweet spot, whatever you want to call it. As for shot #13 dropping in velocity, it's hard to say what happened there, but the key thing is that the shot stayed right in the cluster. As Tony suggested, I'd play around with the charges right in that 12-15 range, looking for something right in the middle. Next step,for me, anyway) would be to settle on a charge weight and start varying the bullet jump, same as you varied the charge weights.

Let us know how it goes.

 

[xdeano]

Thanks guys. It's been windy up here and I had the in-laws over for the weekend. Or LONG WEEKEND! I'll give it a run when I get some good weather. I appreciate the direction.

xdeano

 

[xdeano]

Ok guys I finally got out today to do a test. And after looking at the target I should have went to work instead.

8-5-09
range 300yds
Time 7:30a-9:00a
Temp 52F - 53F
Wind WNW 2 - W 3
Humid 90 - 81%
DewPT 49F - 53F
Mostly cloudy - cloudy
Pressure 30.10' - 30.13'
Shooting west

Left to Right,boxes are 1')

target 1 4.5MOA 175gSMK in clean barrel, fowling shots.

target 2 #11 44.8g Varget 3.75MOA
1 2796
2 2796
3 2804
4 4804
5 2824

target 3 #12 45.0g Varget
1 2802
2 2809
3 2813
4 2820
5 2835

target 4 #13 45.2g Varget
1 2815
2 2819
3 2826
4 2834
5 2815

target 5 #14 45.4g Varget
1 2834
2 2832
3 2805
4 2856
5 2846

target 6 #15 45.6g Varget
1 2833
2 2851
3 2842
4 2856
5 2857

I don't know what's up with target 3, it's all over the place.
Target 6 shows promise, a bit over an inch of vertical.
Let me know what you think.
Thanks
Deano

 

[archerross]

deano,

IMHO targets 2, possibly 3, and 6 show promise, assuming that the shot at 7-0'clock on target 3 was shooter error. If the errant shot was shooter error, I would look at target 3 as it has a 2.25 inch group, but ES = 33.

It appears that target 2 held about a 2 inch group with an ES = 28. I would consider the velocity of shot 4, 4804 fps, a chrono fluke.

Target 6, as you stated, also shows promise with about a 2.75 inch group and ES = 24. My next step would be to adjust seating depth +/- with loads from targets 2, maybe 3, and 6, and see what happens.

BTW, what chronograph are you using?

 

[xdeano]

I'm using a Chrony Master Beta. @ 10ft leveled.
Thanks for the constructive advice archerross.

RJ, I'll take a look at that data. I just pulled the PDF up on the screen.

Deano