Load development made easy.

Discussion in 'Reloading' started by Michael Eichele, Jul 29, 2009.

  1. Michael Eichele

    Michael Eichele Well-Known Member

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    To all at LRH.com,

    The questions arises often about load development. Should I use the ladder test? Should I use the OCW method? The truth is that you can find your OCW by doing the ladder test. If you find your loads OCW by way of the ladder test and you are not satisfied with the groups youre getting, try another powder and repeat the test. The OCW (optimum charge weight) is when you have a load where loaded slightly higher and slightly lower, nail the same point of impact center to center or very close to it. This OCW may or may not yeild the best groups your rifle is capable of but affords you some lattitude when you screw up your scale a wee bit or some other factor alters your loads behavior a bit. It could also be refered to as a "node" or sweet spot of your barrel. In my opinion, there are a couple of different "nodes". There is the highest accuracy node when you find the best accuracy and there is the OCW node where even if 1 MOA is the best it will do, it is a VERY consistent 1 MOA. You can rely on it daily even if the charge weight is slightly different. Idealy, we want both together but dont always get it. Some may choose their absolute most accurate load while others choose the OCW for a more forgiving load. If youre persistent you can often find both together. Attached at the bottome of this post is a picture showing in detail how this works. It is a black and white copy of an actual test at 100 yards during my development.

    You will notice 3 groups with bold arrows pointing them out. These three charge weights offer nearly identical POI's. It just so happens to be that the middle load is the most accurate charge weight. this is the OCW for this bullet and powder. The big plus sign refers to the center of group of the 46.0 load. The hollow circle refers to the center of each group of different charge weights. Notice how both .5 grain up and down from the 46.0 load is of ideal accuracy and the middle of the OCW is the better than expected. When using much larger cases, the load differences may be up to 1.0 grain.

    You can find the same thing IF you are persistent and try a wide variety of powders and bullet weights. It took me trying 9 different powders and 8 different bullet types to find this "sweet spot" Of course after finding this load, I loaded 5 more and tested them in a 5 shot group. The result was a .312" 5 shot group. That is very conclusive for confirming and determining that it is a good load.

    I find the powder my rifle likes best by shooting several powders with several different bullets at several different charge weights. It becomes very evident which powder it likes when you use it. Every bullet it seems can be made to shoot well and some exceptionally well. Once I nail down the powder, I try different bullets with that powder exclusively untill one shines brighter than the rest. In the case of my latest Hart 308 barrel it is the 168 AMAX and 46.0 of VV N540 seated .040" off the lands. The harmonices are unbeatable.

    I hope this helps you understand when shooters refer to "harmonics" and "nodes" or "sweet spots".

    [​IMG]
     
  2. AJ Peacock

    AJ Peacock Well-Known Member

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    Michael,

    Nice write up. It looks like you have a good barrel on that rifle!

    You didn't mention the velocities and the info you're getting from them. I see that you have them written on the target.

    AJ
     
    Last edited: Jul 29, 2009

  3. Frogman77

    Frogman77 Well-Known Member

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    Michael, do you adjust seating depth at all? I know for some thet length of the magazine is the limiting factor but if your magazine allows for seating out to into the lands, where do you start and how do you choose your starting point when doing your load development / finding your OCW?
     
  4. royinidaho

    royinidaho Writers Guild

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    Michael,

    Would it be safe to say that very similar results would be observed for differences in day to day temperature variations?
     
  5. Michael Eichele

    Michael Eichele Well-Known Member

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    Yes. For the test in the picture I had already determined the jump to the lands from prior development. Typically, I look for the best charge weight THEN look for the OACL. It just happened to work out the opposite for this load. I had worked up the 178 prior and determined that .040" off the lands was best. I used the same OACL when I moved to the 168 AMAX. I dont know if it makes a difference or not between the 168 and 178 but I cannot imagine it impoving.

    I tune it the same way Berger recomends.
     
  6. Michael Eichele

    Michael Eichele Well-Known Member

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    That is part of the benefit of using OCW. Effects from temprature are minimized with good harmonics. A velocity increase or decrease may take affect with temprature changes but the rifle's near zero and group typically remains consistent.
     
  7. lever-hed

    lever-hed Well-Known Member

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    in other words the OCW method if done correctly will optimize the charge weight of a particular accuracy node ....
    ie.. if the accuracy node is 45.5-grains to 46.8-grains, and the most accurate charge wt is 46.0, then variations of charge weight due to a very slight missed measurement or temperature /humidity variations will have minimal impact on the bullet flight (according to the optimal charge weight theory).. right? :D
     
  8. Frogman77

    Frogman77 Well-Known Member

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    If you were starting a fresh load do you have a pre determined point on or off the lands that you start at before doing your ladder test? Is it safe to start kissing the lands and doing your ladder test to find your OCW and then working your way off the lands to fine tune your load for accuracy?
     
  9. Michael Eichele

    Michael Eichele Well-Known Member

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    That is correct. Dont confuse this with normal trajectory variances though.

    The arc of the trajectory after your near zero will still change with temp, pressure and humidity but your near zero POI and accuracy will be as optimum as possible.
     
  10. Michael Eichele

    Michael Eichele Well-Known Member

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    Starting fresh I start into the lands and work them back. It is safe to start this way SO LONG as you are staring at minimal charges to begin with and working up. When I recieved my 338 Edge barrel I started at a rediculously low charge weight (83 grains) and loaded up in 1.0 grain increments. One shot each. I fired each load over the chrony to see what charges yeilded what velocities. After seeing that 83 grains was safe and very low I skipped 84 and went to 85, then 87, then 88 and 89. Then I went back to the reloading bench and loaded 3 each of 88, 89, 90, 91 and 92. Knowing that 2700-2800 is the best zone for the 300 grain pills and H1000 in a 28" barrel, I started my "development" at the charge weight that yeilded velocities in the high 2600's and worked up from there. I started into the lands to begin with. The example above also gave me a figure for how much velocity gain there is per grain. You have to be very carefull though doing this when load density reaches close to 100% because once you reach max loads, the velocity increase per grain can jump VERY significantly.
     
  11. lever-hed

    lever-hed Well-Known Member

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    Thanks for that, I understand. That is a nicely executed sampling.

    How many overall shots for each bullet / powder combination did you make to achieve your OCW.??
     
  12. Michael Eichele

    Michael Eichele Well-Known Member

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    The target you see in the first post. That is how many shots. It is the only OCW test I have done for this rifle. It was just such a good example, I thought I would post and share. I have done other development with this rifle, just not OCW. Once I settled on a powder and bullet, then I spend the time to perfect it.
     
    Last edited: Jul 30, 2009
  13. bigbuck

    bigbuck Well-Known Member

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    Michael, Thanks for the post I've always wonderd
    what folks were talking about when they said NODE now I know:) . I think I found it the other day with my 300rum I was using retumbo powder shooting 3 shot groups at 200 yrds.
    I started with bergers load data the only thing that's got me confused is my gun seems to like the lowest load recomended. I shot 3 different powder charges under 1'' at 200 yrds the best group was .318 at 200 yrds and it was the lowest powder charge on the chart 85.5 grains of retumbo. Do you know why this is ? I just can't make myself change when it's shooting so good at the lower charge weight . one last thing my barrel only has 97 rounds down the tube.

    bigbuck
     
  14. Michael Eichele

    Michael Eichele Well-Known Member

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    What velocities is that charge giving you?