A load workup session that shows what should happen.

A load workup session that shows what should happen.

This is a discussion on A load workup session that shows what should happen. within the Rifles forums, part of the Sniping Related category; Yesterday I went to the range with the intent of finding the absolute best load for my rifle using Lapua brass, Varget, Br-2 primers, and ...

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Thread: A load workup session that shows what should happen.

  1. #1
    Senior Member deadshot2's Avatar
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    A load workup session that shows what should happen.

    Yesterday I went to the range with the intent of finding the absolute best load for my rifle using Lapua brass, Varget, Br-2 primers, and 175 SMK's. My old data fro this powder was obtained using the original barrel so it was outdated.

    I decided to use the OCW method of three rounds per charge weight and worrying only about group size rather than hitting a specific point of aim.

    The aim point for each of groups was the center of the paste-on spot.

    I had 25 cases prepped for this test so I started just above the published start load at 42 gr. I increased loads in .4 gr increments which is around the recommended 1% increase.

    Here are the results:

    Varget Lapua Brass BR-2 175 smk load workup.jpg

    My rifle has a fairly heavy barrel (Benchmark #7) profile so I didn't bother with the OCW suggestion of shooting this test "Round Robin". I just shot three groups of three, took a "pause for the cause", BS'd with some fellow shooters, then came back and shot the next three groups. Repeated the break process.

    As you will note, the first group was somewhat scattered. As the charge weights increased the groups took different forms and moved around somewhat (up/down, and sideways) from the aim point reference. When I hit 43.2 grains things started to look great. A group that measured .232" or .222 MOA.

    Since this was substantially below maximum and there wasn't a single pressure sign, bolt lift effort, primer flattening, etc, I kept shooting. Next group scattered which was good. It told me I had passed a node that was pretty much dead center between the one before and the one after. As they say on TV, "But wait, there's more!" At 44.0 grains the group size dropped to .184" or .176 MOA. Each of the three bullets in this group hit within .079" of the exact same point (Average to center). Again the next groups scattered telling me that I have TWO accuracy nodes, each about .8 gr apart.

    For my next "Test" I will load a few cartridges with charge weights .2 gr above and .2 gr below these two "sweet loads" just to verify that I've hit them dead on.

    I realize that for the "Old Hands" this is pretty much routine for them but since this target with all 8 groups came out looking nice and neat, and the effect of the different charge weights was so graphic, I thought I'd post it for those who are just beginning.

    For someone just starting out, this is a great way to find out what the "sweet load" is for your rifle without burning up more than a couple dozen rounds worth of components. After a test like this you'll know where you need to work rather than searching the web for everyone else's "pet loads" and then end up tearing your hair out because your rifle isn't behaving like yours.

    I didn't bother to set up a chronograph for this test session as I'll save that for a future session. First, shooting 3-shot groups are only good for finding accuracy nodes. Far too few shots for any chronograph "stat's" to be meaningful. When I settle on a load after the next "verification session" I'll then shoot at least 25 rounds over the chronograph (sometimes I shoot up to 50) so the sample size is sufficient to give me more exact Average speed, Standard Deviation, and my favorite, Mean Average(Absolute) Deviation. First the accuracy then the ballistic's data for shooting at variable distances.


    BTW, I usually like to shoot tests like this at longer ranges. Easier to sort out the better groups when fine tuning. Right now my club's range is undergoing a major renovation (first in 30 years) and the long range facility is closed for another three weeks. Right now I only have 100 yards available so I decided to do some fine tuning so I have good loads on record for all the component combo's I have in stock. Any excuse to go shooting you know
    exsimguy1, mike.h and Boltfluter like this.

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    Senior Member mike.h's Avatar
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    Not to take away from the big picture of load development, but I do have a question. On your write up you wrote varget, on the paper Imr4064.

    Thanks for the write up
    Last edited by mike.h; 09-13-2014 at 10:33 AM.
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    Senior Member deadshot2's Avatar
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    Quote Originally Posted by mike.h View Post
    Not to take away from the big picture of load development, but I do have a question. On your write up you wrote varget, on the paper Imr4064.

    Thanks for the write up

    Thanks for proof reading for me. The upper left "dot" was my sighter/fouler target and I shot a group using the IMR 4064 at that one as well. Had a few minutes before the rest of the "line" was ready for a cease fire so I could collect my target so I finished up with what I had left in another box.

    To clarify, the entire OCW test was shot using Varget.

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    Senior Member mike.h's Avatar
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    Ok, thanks
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    the entire OCW test was shot using Varget. how this !!

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    The natural variation induced from a human shooter presents a lot of statistical noise in your group size data which is only a factor because it looks like you have a rifle that will shoot just about any got-dam thing into a bughole. I suspect that what you're seeing as nodes are actually you hitting your stride for a group. I would really re-shoot that at 200 or 300 and see what you get.

    BTW, good shooting and clearly a nice rifle. It takes a heckuva shot with a heckuva rifle to make it so that you have to back the hell up to double or triple the normal load dev range in order to pick the right one.

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    Senior Member gpark09's Avatar
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    Now, I don't want to be a party pooper. But, I wanted point out that whole point of OCW is to find a charge/node where variation of speed is minimum, isn't it? Another word, the lowest SD/ES is what we are trying to achieve.

    Here, we don't even have the chrono read at all. They'res just bunch group sizes for different charge weights. The group sizes can be changed at different environmental situation because the harmonic will change.

    It's the stabilized node we are looking for in OCW, don't you think???
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    I decided to use the OCW method of three rounds per charge weight and worrying only about group size rather than hitting a specific point of aim. Tutuapp 9Apps ShowBox
    Last edited by blankoya; 12-30-2019 at 04:56 PM.

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    Nice shooting!

    Paul

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    My load dev was as follows for my 6.5CM and my 308Win.

    I've done 3 round tests in .3 grain intervals during load development across the min and max load ranges.

    When I saw a range of nominal vertical dispersion, I would do more test 3 round test firings in .1 grain intervals starting just below and just above the previous good groups. Once I've bracketed the node, I pick a load around the lower third of the good group range.

    Then I Chrono that load for my ballistics app. I don't want to guess my chrono speed although I guess you can back into the speed using impacts at distance. From my perspective a Chrono is well worth the investment. My AO is in a relatively warm part of the country South FL but its likely i'll shoot in colder temps during hunting season. I pick the lower third instead of the middle of the node as it is my understanding that the node will shift downward as the temperature gets colder. My temp variations have only been around 50-60 degrees as its been unseasonably warm in the Pittsburgh, PA area where I've hunted for the last the last 10+ years give or take. All my shots on meat have been under 200 yds. My groups up Norte remained snug so I think I might have it right. I do plan to head out west for an Elk and Mulie hunt as some point so impact of change in temp and altitude will need to be addressed better than just taking what the ballistics app tells me the solution should be. Shots out there might likely be out to 400-600 yds.

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