308 ladder test

[crbrumbelow]

I am re-evaluating my load for .308 and loaded 25 rounds,5 shot groups) from 45.4 to 45.8 gr. of Varget with Berger 168 VLD seated into the lands, oh yea and prepped Lapua brass. Since I cant seem to upload photos I need to describe each group.

45.4 nice cluster .5 inch printed at 6 o'clock of my target,a 1 inch square) standard dev.-11

45.5 again .5 inch at 7 o'clock sd - 8,45.5 has consistently given less than .5 inch groups with fire formed brass)

45.6 .75 in. at 9 o'clock sd 23,three shots group well 2 shots higher on paper more at 11 o'clock)

45.7 .5 inch at 9 o'clock again but group moved more to a center location above 6 o'clock . Sorry that's the best way I can describe it. sd 26

45.8 .75 in. 3 rounds dead on 9 o'clock 2 rounds above 6 o'clock just as 45.7. sd 32 horrible.

As quoted by Lynn from another thread: "As you incrementally increase your powder charge the bullets should start low and go up.When you reach a plateau the bullets tend to go to the right somewhat and roll-off very slightly.After that the bullets will center up again and hit higher.
If your a good note taker and watch your conditions like a hawk you will get great accuracy from the load that went slightly right and rolled-off."

The way I view these groups is that 45.5 is the "roll off to the slightly" load. It also gave the lowest es and SD with 45.4 and 45.7 close behind. Am I correct in choosing this load. I have never done ladder testing but I like the theory and it definitely helped my .22-250 but the variations were easier for me to see in the .22-250. If I shot all the above listed loads at the same bull the group would not be over 1 inch and to me that is outstanding considering the nearly .5 grain difference in charge weight.

 

[Asa_Yam]

Nice reporting - but I am sorry to say what you conducted wasn't a ladder test.

A true ladder test shoots a series of rounds, each with a different charge weight. The resulting shot pattern is spread vertically, but not evenly. A,theoretical) 17 shot pattern,17 different charge weights) might look like:

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Notice the clusters in the vertical stringing? If such a pattern results from charges with a similar charge weight,+/- a few tenths of a grain), you have a fairly stable load.

Hope this helps.

 

[crbrumbelow]

Maybe ladder test is the wrong terminology. I did it according to Dan Newberrry's article http://www.clik.to/optimalchargeweight What I am seeking is to make sure I read the results right and to see if you guys concur.

 

[crbrumbelow]

So Asa, in the example you show. I would chose the middle load of the string that shows three rounds horizontal because those charge weight are "compatible". Hmmm I like that a little more. How do you go about tuning more. Just seating depth, maybe a primer change.

 

[Asa_Yam]

Re: tuning. Sorry, I don't know, since I shoot a different game,prone long range). In this sport, some bench test - I shoot everything from position @ 300 yards. My test,not a ladder test) is if it holds 10 ring,called fliers excluded) for 10-20 shots, it's a decent load for my purposes.

In contrast, the late Creighton Audette's ladder test I described was supposed to show where to find a "stable" load. "Stable" as in accurate enough, yet capable of showing where reasonable groups could be found despite variations in charge weight. If you're shooting a LOT of ammo a year,~2000+ rounds/year) in competition and practice, you don't want to be constantly testing loads. For starters, you might not have the time. Or the barrel life.

One possible analysis of my 17 "shot" series is that the lower cluster of 6 shots shows promise,the 2: 3: 1 pattern group above the "shot" from the bottom). If these six shots came from a consecutive series of shots, there's probably a load worth trying in there. Or if the group is small, and the charge weight wide enough, just throw charges from the measure set to the middle of the range.

Some may tend to discredit the Audette test - it was developed over 30 years ago, after all. However, Mr. Audette was a very smart individual, who experimented carefully and took very good notes, so there is a considerable amount of sound reasoning behind it.

Hope this helps.