Interpreting load ladder results
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  1. #1
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    Default Interpreting load ladder results

    OK, I'm working up loads in .308. Here are the results of 4-round groups, shot round robin over two different shooting sessions (2 rounds each on day 1, 2 each a few days later) due to rain:



    This was 168gr SMK and virgin Lapua brass in my AR308 with 18" barrel. Red dot is a 1" circle, next circle is 2" diameter, then 3" and so on (so, 1/2" in between lines).

    To me, it looks like there is a sweet spot in the range between 44.0 and 45.0 grains of Varget.

    What would you suggest I do from here? Load another ladder with 0.2 grain increments between 44.0 and 45.0?

  2. #2
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    load 45.0 (or 44.9) and, if it repeat, call it done. The fact that these groups were shot at two different range sessions is telling.
    "To anger a conservative, lie to him. To anger a liberal, tell him the truth." - Theodore Roosevelt

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  3. #3
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    Don't know what kind of accuracy you are looking for but I would run the 45 grain load and play with seating depth and see if it'll dial in tighter.

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  5. #4
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    I never look for groups with virgin brass as I want to load and fire form it before I expect anything to come to fruition. Virgin might perform but you will not get good results till it has been at least fire formed or twice shot.
    I also do not put any load data together unless it is shot same day, same conditions. Wind can vary as pressure and temperature.


    Just wait till next season!

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    Quote Originally Posted by Subeng View Post
    play with seating depth and see if it'll dial in tighter.
    Quote Originally Posted by CaptGrumpy View Post
    never look for groups with virgin brass ... Virgin might perform but you will not get good results till it has been at least fire formed or twice shot ... do not put any load data together unless it is shot same day, same conditions. Wind can vary as pressure and temperature.
    Both Subeng and CaptGrumpy make good points.

    - Seating depth is an effective lever to adjust group size. Look for Optimum Charge Weight first then adjust COAL in 0.010" to 0.015" increments to refine.
    - Its ok to develop loads in virgin brass but understand when you run out, you likely will have to adjust your load again for once-fired, then again for twice-fired. Never take a load developed in fire-formed brass and use it in virgin brass as its pressure will be higher. For that matter, never take a load developed in fire-formed brass from one manufacturer and use it in a different manufactures brass as its pressure could be higher.
    - for my hunting loads, I look at its true accuracy potential by firing 2-shot groups at the same sheet of paper over multiple range session. This gives me a better indication how my rifle/load will perform during any given hunting day.

    But, CaptGrumpy is correct. For this assessment, we need to see a picture from day one only. Can you post that?
    "To anger a conservative, lie to him. To anger a liberal, tell him the truth." - Theodore Roosevelt

    "The world is a dangerous place to live; not because of the people who are evil, but because of the people who don't do anything about it." - Albert Einstein

  7. #6
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    I appreciate the comments so far. Interesting that you both seem to gravitate to 45.0 gr as the most promising group. Is that because the grouping is good and presumably the velocity is higher? Vertical dispersion seems to be the least between 44.0 and 44.5 with 45.0 being just a touch behind.

    Regarding the virgin brass, I figured I might as well work up a load and go through the ladder process as a learning exercise (I'm obviously new at this) and to see what I can achieve with the brass anyway. This is through an auto loader, so I'll full length size the brass and will work back up with the once fired. I also just receive 500 full processed Lake City cases from Texas Brassworks so I'll do the same with those.

    My camera battery died on day one so I don't have a picture of the first two shots. However, I marked each shot so I know which is which. I'll label the photos and re-post after work. Weather was very similar between the two shooting sessions (maybe 5 degrees cooler on the second session). Pretty calm wind, high humidity, and around 60 degrees. But like xman noted, the fact that the day 2 shots were right on top of the day one shots seem like a good sign. Again, these were all shot round robin and I was getting off the gun between each shot anyway. I did have the gun bagged up, but I'm sure not as firm as you guys would.

    I'm looking / hoping to get around 3/4 MOA consistently with this rifle, but frankly that's probably pushing the limit of my current shooting skills anyway.

    I'm thinking I might do 44.0, 44.3, 44.6, and 44.9 and shoot at 200 yards and see what that tells me, but I'll probably switch over to load dev with the LC brass and shoot that for a while and save the Lapua until I'm a bit more experienced at this.

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    Quote Originally Posted by Xman View Post
    Both Subeng and CaptGrumpy make good points.

    - Seating depth is an effective lever to adjust group size. Look for Optimum Charge Weight first then adjust COAL in 0.010" to 0.015" increments to refine.
    - Its ok to develop loads in virgin brass but understand when you run out, you likely will have to adjust your load again for once-fired, then again for twice-fired. Never take a load developed in fire-formed brass and use it in virgin brass as its pressure will be higher. For that matter, never take a load developed in fire-formed brass from one manufacturer and use it in a different manufactures brass as its pressure could be higher.
    - for my hunting loads, I look at its true accuracy potential by firing 2-shot groups at the same sheet of paper over multiple range session. This gives me a better indication how my rifle/load will perform during any given hunting day.

    But, CaptGrumpy is correct. For this assessment, we need to see a picture from day one only. Can you post that?
    I agree with everything here--- 45.0 and try changing COAL

    Quote Originally Posted by BoilerUp View Post
    I appreciate the comments so far. Interesting that you both seem to gravitate to 45.0 gr as the most promising group. Is that because the grouping is good and presumably the velocity is higher? Vertical dispersion seems to be the least between 44.0 and 44.5 with 45.0 being just a touch behind.

    Regarding the virgin brass, I figured I might as well work up a load and go through the ladder process as a learning exercise (I'm obviously new at this) and to see what I can achieve with the brass anyway. This is through an auto loader, so I'll full length size the brass and will work back up with the once fired. I also just receive 500 full processed Lake City cases from Texas Brassworks so I'll do the same with those.

    My camera battery died on day one so I don't have a picture of the first two shots. However, I marked each shot so I know which is which. I'll label the photos and re-post after work. Weather was very similar between the two shooting sessions (maybe 5 degrees cooler on the second session). Pretty calm wind, high humidity, and around 60 degrees. But like xman noted, the fact that the day 2 shots were right on top of the day one shots seem like a good sign. Again, these were all shot round robin and I was getting off the gun between each shot anyway. I did have the gun bagged up, but I'm sure not as firm as you guys would.

    I'm looking / hoping to get around 3/4 MOA consistently with this rifle, but frankly that's probably pushing the limit of my current shooting skills anyway.

    I'm thinking I might do 44.0, 44.3, 44.6, and 44.9 and shoot at 200 yards and see what that tells me, but I'll probably switch over to load dev with the LC brass and shoot that for a while and save the Lapua until I'm a bit more experienced at this.

    on 1x fired lapua brass you may find your accuracy node a few tenths higher than 45.0 due to the larger case ---make sure to only bump that shoulder 2-3 thou so you don't over work the brass

    ----be careful when you switch over to LC 7.62 brass---- you will probably end up with 1-1.5 grains less than your Lapua brass load as the 7.62 LC brass is much thicker than any other brass ( it is often slightly "harder" than others also)--- also pay attention to the LC head-stamp year, weights/thicknesses can change from year to year on LC brass---best to weight sort your brass for maximum accuracy
    also the Lapua brass is going to be much more consistent than the LC brass--- on my LC brass I weight sort, I also ream the primer pockets, de-bur the flash holes, remove the PP crimp, anneal the necks every 2-3 loadings ( usually at 1x and 3x fired) and neck turn for a consistent neck thickness---in my auto loader I get 5-6 loadings from the LC brass before I start to see signs of case head separation and then I toss them before I have issues--I also run my reloads at the top end of the book loads


    checking and adjusting the concentrically of loaded ammo can help quite a bit for accuracy too

    LUCK
    is the residue leftover when you subtract chance from preparation.



    If you reload, turn a flat based bullet around and seat it backwards in the case with apx .170 of the full dia part of the bullet left outside the case. Chamber it. If it chambers you have a SPCII. If not start seating the bullet deeper. If the full diameter part of the bullets ends up apx .070 out it is a SAAMI chamber.

  9. #8
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    OK, here we go with sequential shots. Red 1, Blue 2, Green 3, and Purple 4. Again, this was shot round robin so all the 1's were shot sequentially, then the 2's. About 2's later was the 3's and then the 4's. A few minutes between shots on a cool day. While 45.0 grains has the tightest group (about 0.6") all of that is in the vertical. However, 44.0 and 44.5 have the tightest vertical dispersion (0.3"). It seems to me that if I move back to 200 yards that tighter vertical is going to lead to better groups. Is that faulty logic? 0.5 grains is pretty large increments here, too, but Varget seems to be pretty forgiving in .308.


  10. #9
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    Quote Originally Posted by BoilerUp View Post
    this was shot round robin so all the 1's were shot sequentially, then the 2's .....
    I've read several places where they say you have to shoot sequentially but I found it was too easy to make a mistake and shoot the wrong load at the wrong POI or, like you had, something interrupted you and you had to end your session resulting in every group you shot being incomplete. I shoot the one load then move on and it has worked fine for me. Plus the wind and environmentals are more consistent for the group if you shoot the load together then move on.


    Quote Originally Posted by BoilerUp View Post
    While 45.0 grains has the tightest group (about 0.6") all of that is in the vertical. However, 44.0 and 44.5 have the tightest vertical dispersion (0.3"). It seems to me that if I move back to 200 yards that tighter vertical is going to lead to better groups. Is that faulty logic? 0.5 grains is pretty large increments here, too, but Varget seems to be pretty forgiving in .308.
    Yes, Varget is pretty forgiving in .308 and .223. I once shot a ladder with 77 SMK in a 24" match barrel from min to max load data. All 24 bullets from the ladder fit in an inch square.

    You logic on dispersion is reasonable. But as I look at your results (thanks for posting the second picture), I began focusing on just shots 3 and 4. I now do my ladders with single charge weight per shot or 2 shots at the same charge weight (which looking at just 3 and 4 would be). If you know your rifle is capable of 1 moa or better, this type of ladder for load development can help save time and resources. I mark and look at the POI of each shot and see if sequential loads will group under 1 moa, i.e, if three shots separated by 0.5 grains of powder shoot under an inch, think how good the group would have been if all three shots were the same middle charge weight. It doesn't work all the time but 75% of the time I can have a 1 moa hunting load developed and verified in 7 shots.

    It looks to me like your rifle can do this also. Shots 3 and 4 are are pretty consistent across the bottom row. Based on your latest post, I think I would load 44.5 grains as the OCW.
    "To anger a conservative, lie to him. To anger a liberal, tell him the truth." - Theodore Roosevelt

    "The world is a dangerous place to live; not because of the people who are evil, but because of the people who don't do anything about it." - Albert Einstein

  11. #10
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    Thanks, Xman.

    Regarding shooting round robin: given I'm pretty new at this, I don't really have a set routine just yet, but shooting round robin appealed to my inner engineer. The color coded brass (with Sharpies) and targets is working well for me to keep track of which load I put on which target, but it does create some additional "administrative" work. On top of that, I'm not the most consistent shooter (yet!) so having a sample size of at least 3, if not 4 or 5, I believe will help me interpret the results despite pulling an occasional shot. Perhaps when / if i have more confidence in both the equipment and the shooter I could get by with one or two shots per rung. I'm quickly building confidence in this rifle, though. Splitting this shooting session up over two days was not planned, but the fact that rounds 3 and 4 are generally in line with 1 and 2 actually gives me more confidence in the rifle and the results of this ladder so I'm kind of glad it happened.


 

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