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Old July 27, 2012, 02:56 PM   #1
browninghunter86
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168gr Amax Development

Rifle: 308 Win Savage 10 FXP w/ 22" sporter barrel
Stock: BC Medalist A2
Caldwell Bipod, rear sand bag

Brass: Virgin WW
Primer: Federal 210M
Powder:Varget
Bullet:168 AMAX
OAL:2.2880"(2.240" ogive)

**200 Yard Initial Ladder Test and to test actual max load**
93 Degrees: 5-8 mph wind: overcast
Load 1: 43.0
2: 43.3 called pull on this shot as soon as it broke
3: 43.6
4: 43.9
5: 44.2
6: 44.5
7: 44.8
8: 45.1
9: 45.4
10: 45.7
11: 46.0

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Old July 27, 2012, 03:53 PM   #2
Ike666
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Browning,

Not sure what you were attempting to do with this, but one round at each load tells you virtually nothing.

Was the first round a cold bore shot, or had you fired some fouling shots? If not, then it isn't even comparable to the other hits (but it was closest to your point of aim - the blue dot, yes).

Did you clean the bore between each shot?

Did you let the rifle cool between each shot? Hard to do on 93 degree day, huh?

I would say that one thing you might glean from this is that as the loads got hotter (and the barrel too?) POI started to climb up and left.

Since these are all different loads this won't mean much but:

Max spread: 5.851"
Mean to Ctr 1.924"
Grp Width 3.632"
Grp Height 5.505"
Horiz Offset 2.646"
Vert Offset 2.588"



Try the same thing with at least 5 rounds per load level; fire at least three fouling shots before you start up the ladder; use one target per load; swab the barrel one time (I use a light patch of Gunzilla); let the barrel cool after each 5-round group at least until it is no more than warm to the touch.

You got the idea, now make it work for you.
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Old July 27, 2012, 04:46 PM   #3
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I know 1 shot doesn't tell you accuracy or group size. I was mainly testing for max load and also trying to see if I could get a general idea where to look at(same POI for 3 shots) for potential accuracy nodes

Shot 1 was my 3rd shot of the day---first two were on different target to zero scope in. Barrel was not cleaned between shots. Barrel was covered with towel and let cool 8 -10 minutes after each shot
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Old July 27, 2012, 05:30 PM   #4
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BH,

At a glance, I'd be trying a larger group of load #8 first.


Ike,

He's firing an Auddette Ladder, which is normally done with one shot per load with the idea of spotting a flat or a slight reversal of climb in a load progression, ignoring horizontal spread altogether. There's a description by Randolf Constantine in the second half of this old page. There is an example here wherein I helped someone use this method and it worked out despite the scatter (start on about post 13). I like the Newberry round robins better myself, which uses only three shots per charge weight, but which is based on three sets in a row having the same POI, which means you are effectively evaluating a nine shot group for better statistical confidence than a three shot group has. It does take more time and shooting than an Auddette ladder, but the evaluation is less difficult where scatter is present.

Follow-up:

I used the size of the holes to scale the target photo approximately and pull some measurements off of it. The numbers are probably not exact, but will be proportional. I applied a polynomial trendline in Excel and verified shot 8 is where the elevation flattens. It looks to me like the pulled shot is 5, being too low to make sense, but not spoiling the trend identification. If it were on the trendline, shot 7 might pull in as the favored load. You could always split the difference and try halfway between 7 and 8.

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File Type: gif Browninghunter Ladder.gif (13.7 KB, 151 views)
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Old July 27, 2012, 05:37 PM   #5
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thanks Nick. First time firing a ladder test and think it actually worked for me. I was using it first then was going to do OCW from where I thought the nodes are


Think will load 7,8,9 high node and 3,4,5 for the low node?
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Old July 27, 2012, 09:19 PM   #6
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It won't hurt to try 3, 4, and 5, but I think that flat area may be a fake. I had to go to a 6th order polynomial to get the upper flat line clear. If I drop back to a 4th order fit, eliminate the second shot, which you know was pulled, I lose much of the first flat spot. If I really stick my neck out and push the fifth shot up where it would be expected fall on a perfect Audette ladder to eliminate that big jump from 5 to 6, which looks improbable to me, then the first flat spot almost dematerializes. But try it anyway. By the time I've pulled #2 and inferred where #5 should be, the integrity of the data is pretty much spoiled.
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Old July 28, 2012, 12:11 AM   #7
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Why did you stop at 46? Looks like you could have been getting close to another node if you went higher.



sudo apt-get update
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Old July 28, 2012, 01:00 AM   #8
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have you considered different powder with this same test? How about some IMR4064? I worked with varget in my 308 win and was unable to come up with good groupings.
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Old July 28, 2012, 11:02 AM   #9
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mrawesome: max for 168 in Hornady was 44 and Hodgdon was 46.0 and Sierra was 43.5gr so I wanted to be safe since I was loading them only 0.015 from the lands.

At 46 bolt lift was ok and primers looked good. I wish I had a chrony to tell me where I am at velocity wise

Nick: thanks
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Old July 28, 2012, 11:39 AM   #10
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I see.

A chrono is nice to have. Es and sd should be pretty low at the 7, 8, and 9 range.

Have you tried IMR4064? Basic same burn rate as Varget, but longer sticks that give better case fill. IMR4007ssc might be worth a try also.

sudo apt-get update
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Old July 28, 2012, 01:27 PM   #11
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next time I place order I am going to order 4064 and some other staple go to powders.
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Old July 29, 2012, 12:16 AM   #12
Jimro
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I would load up 3 rounds each of 7, 8, and 9 and shoot them for a single group at 100. If that was acceptable accuracy I would stop load development and go shooting with load 8.

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Old July 29, 2012, 12:40 AM   #13
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^^^ Great advice.

A chrono would make it even easier. The loads with lowest es will be the most accurate.

8 should work out quite nicely.

Some groups and CHRONO!!! readings will confirm it

sudo apt-get update
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Old July 29, 2012, 07:06 AM   #14
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Browning

I went back and looked at some of my targets from when I tested Varget. All of my light (low) loads with varget were just about on center with my aiming point, just like your first shot. As the loads I made got higher in powder charge the further they moved to the right from the aiming point. When I tested with IMR4064, everything was on center and the groups got smaller as I went up in charge, just seems to me thats what might be happening to you. Without testing at least 3 shot groups and 2 different powders, you will never know!

My .308 test loads were all 180grain Hornady SST 1:10 twist BBL H&R single shot.
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Old July 29, 2012, 07:23 AM   #15
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Unclenick, do you a spreadsheet you could share where I could simply drop in the range data and get to the same conclusion you are? For those of us less mathematically skilled...Namely me.. I read your older Post from 2006, looks like you spent considerable time on that.
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Old July 29, 2012, 10:27 AM   #16
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Hopefully will be able to go shoot the groups of 7,8,9 today and report back.

Why should I shoot them at 100 now? Not 200 like the first target? Just curious


Thanks
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Old July 29, 2012, 02:11 PM   #17
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not what I expected to see out of these loads. Not sure what happend...(unless my eyes are just bad) these don't look to be same POI. Shot same as yesterday with hardly any breez at 100 yards with 95 degree. Shot round robin and allowed 5 minutes between each shot. Not sure but the barrel stayed hot to the touch the entire time so maybe that had something to do with it.
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Old July 29, 2012, 05:02 PM   #18
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Looking more like #7 than #8, there, but its just three shots, so its not certain. The extreme spread of just three shots, with 95% confidence,could vary over a 6:1 range and the difference all be due to randomness. Below are the group size ratios expected for 95% of groups with the same number of shots in them for different numbers of shots per group. 5% of future groups with the same shot count will fall outside these limits.

Code:
Shots   Ratio of largest to smallest due to random error.
 3	6.080
 4	3.143
 5	2.351
 6	2.002
 7	1.802
 8	1.673
 9	1.585
10	1.519
11	1.468
12	1.428
13	1.394
14	1.367
15	1.345
16	1.324
17	1.307
18	1.291
19	1.279
20	1.267
21	1.256
22	1.246
23	1.237
24	1.229
25	1.221

Despite that, if you decide just to believe the 3-shot results, I'd sure be retrying 5 and 6, too, on the theory 5 was tossed, just to be sure.

4064 is a top .308 accuracy powder, as is Reloader 15. I'd consider both, though Varget usually does well in .308, every gun seems to be a law unto itself.


1stmar,

I did the 2006 stuff using Mathcad, which has more sophisticated solvers than Excel does. To attempt something equivalent in Excel I need to be able to pass the trendline solver equation as an argument for differentiation, or else write my own solver. But I've never learned the Visual Basic used to write custom macros in Excel, so I don't have such a spreadsheet developed.
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Old July 29, 2012, 05:06 PM   #19
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Don't fret, look at the geographic center of each group! Your 7,8,and 9 powder levels have a very consistent center of group area. As the charge increased the group opened up, but the center of the shot group stayed relatively constant. There is a slight movement to the 1 or 2 o'clock position, but not enough to worry me.

What that tells you is that you are leaving a vibration node on your barrel from your #7 charge weight.

For what it is worth, I struggled to get results with Varget and switched to IMR4064 and haven't looked back. But it looks to me like you should look for accuracy around your #7 charge weight. I'd dial it in by .2 grains now, up and down, and see if they group tight together.

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Old July 29, 2012, 06:22 PM   #20
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thanks for the help everyone. I need to download a program to plot my groups and thier centers and the measurements.

Ok so is the verdict work with the #8 load or the #7?

Am I at the point to adjust seating depths or am I still on the charge weight step?


Also the #1 shot on the top target was my second shot of the day(first was to sight in from 200 yard I shot yesterday to moving into 100 today). Do I need to shoot more shots prior to shooting the charges for my testing?

I really appreciate y'all taking the time to work on this with me
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Old July 30, 2012, 02:00 PM   #21
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I always run 10 shots to settle the barrel before grouping seriously, but even 2 can make a significant difference. The exception is a gun I want the cold barrel shot data for, such as the first shot for hunting. Then I set up targets one, two and three, always shooting them in the same order in fairly rapid succession, then cleaning and cooling after the third shot. This is to simulate a cold clean barrel shot and two quick follow-ups. If the group centers move on the three targets, then you're at least aware of how much to hold off for each.

I think your at the point of verifying #7 is what you want to load by firing a larger group than just three. You could fire 15 into one hole, and if the size is still lower than 8 or 7, then you've verified 7 is genuinely the better load.

As to tuning seating depth, you could go ahead and do that even if you think the load may move a little. The optimal seating depth won't likely be very different for other loads, so a little further fine tuning is probably all you'd have to look forward to even if you shifted the load slightly.
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Old July 30, 2012, 06:08 PM   #22
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Here is something to read

http://www.washtenawsportsmansclub.o...incredload.pdf
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Old July 30, 2012, 08:01 PM   #23
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I can't believe this is the first time I am reading about this, why is this not more commonly used? My load development technique is virtually the same as what he calls out in the beginning of the article.
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Old July 31, 2012, 12:57 AM   #24
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I read this article the other day too not sure how I found it. OCW method is good too but uses alot of components to find the accuracy node. I think a ladder test initially then followed by OCW method to verify/fine tune the load would work great
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Old July 31, 2012, 09:38 AM   #25
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Keep in mind the Auddette ladder is premised on identifying vertical dispersion, so it works best with a heavy floated barrel and only with a barrel whose bore line is above the recoil center of pressure (as conventionally configured rifles have). The OCW looks for stable POI even if its off the vertical axis, and also looks for width of the stable load range to be sure you aren't sticking yourself with a condition sensitive load, making it more universal.
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