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Author Topic: Long range load development at 100 yards.  (Read 93106 times)

Offline Erik Cortina

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Long range load development at 100 yards.
« on: 09:23 PM, 05/05/13 »
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  • I found this target, and I think it's a perfect example of how some people might choose the wrong load because they fell in love with a group without reading the groups properly.  This target was shot with my 6.5x47 Lapua and 139 gr. Lapua Scenars with VV N550 powder.

    At plain sight, 38.5 gr. appears to be the best group, but if you look at the groups next to it they don't hit the target on the same place vertically in relation to the bull's eye.  The load is not stable and this load would cause problems when moving further out because it is not inside the accuracy node.

    However, loads 39.5, 40.0, and 40.5 are vertically in the same place in relation to the bull's eye.  This is the accuracy node for powder charge, my next step would be to load 40.0 gr. and adjust seating depth and bring the group in and done, I now have a load that would shoot out to 1,000 yards.  Also, when the groups line up vertically, the speed also varies very little over the chronograph for the loads that line up on target, it appears that the speed flat lines for a while before it starts to jump up again, this is where you want to be.

    Update:  9/17/14
    Some of you have asked for more detailed instructions on how I do this.  Here they are:
    1.  Find Jam by seating a bullet long on a dummy piece of brass (no primer nor powder) and apply die wax to the bullet ogive and record it's base to ogive length. 
    2.  Chamber the round and close the bolt. 
    3.  Snap the bolt open and measure the base to ogive measurement.  If it is shorter than previous measurement, this is your jam.  Do it a few times with different cases to make sure.
    4.  Load a known powder/primer/bullet combination.  I load 4 of each powder charge in 0.5 gr. increments and seat bullets at jam - .020".  I use one shot of each to get barrel fouled up and also keep an eye for max pressure at the same time.  You can also use these rounds to break in a barrel if you are inclined to.  If I encounter pressure on the hotter rounds, I will not shoot groups with the other loaded rounds and will pull bullets when I get back home.  Do not shoot in round robin style because position and natural point of aim will be compromised.
    5.  Shoot 3 shot groups starting from lowest to highest.  All groups are shot over a chronograph.
    6.  Examine target and find the place where consecutive groups line up vertically and ES is the lowest and speed increases the least from one group to the next. 
    7.  Load to the middle of the powder node and do a seating depth test.
    8.  Load 3 shot groups starting from Jam - 0.005" all the way out to Jam - .040" in .003" increments. 
    9.  When you find the seating depth test that shoots the best, load towards the longest side of the node to allow more room for throat erosion.
    10.  Final step is to load the new seating depth and load 5 shot groups in 0.1 gr. increments 0.5 gr. on each side of node (if pressure limits are not reached).  This will cover an entire grain of powder  and you will be able to pinpoint where the powder node starts and ends.  In the summer, load towards the low end of the node, and do the opposite in the winter. 

    HAPPY SHOOTING! 



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    « Last Edit: 08:15 PM, 09/17/14 by Erik Cortina »
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    Online trailrider121

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    Long range load development at 100 yards.
    « Reply #1 on: 09:48 PM, 05/05/13 »
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  • My consensus with you Erik on accuracy load. Would you recommend adjusting seating depth at 100 yards or move it out to say 300 yards? More pragmatic at 300 yards would be best and give better feed back on what the load is doing. If 300 yd not available, the 100 yd would work with careful examination.

    Offline Erik Cortina

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    Long range load development at 100 yards.
    « Reply #2 on: 09:54 PM, 05/05/13 »
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  • My consensus with you Erik on accuracy load. Would you recommend adjusting seating depth at 100 yards or move it out to say 300 yards? More pragmatic at 300 yards would be best and give better feed back on what the load is doing. If 300 yd not available, the 100 yd would work with careful examination.

    I used to do the seating depth at 300 yards, but now I do it all at 100 yards since I have found that if it shoots well at 100, it will shoot at 300.
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    Offline memilanuk

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    Long range load development at 100 yards.
    « Reply #3 on: 09:54 PM, 05/05/13 »
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  • Hello Erik,

    Looks very similar to the concept employed when doing Optimal Charge Weight tests - the raw group size is less important (at least initially) than finding a 'node' where the vertical center of the groups is stable over several powder charge increments.  Also typical is the 'scatter' group (39.5) immediately preceding the node.  Once a node is identified, subsequent fine-tuning of seating depth, neck tension, etc. for accuracy is usually pretty straight forward.

    Monte
    « Last Edit: 09:56 PM, 05/05/13 by memilanuk »

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    Long range load development at 100 yards.
    « Reply #4 on: 10:05 PM, 05/05/13 »
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  • Gotcha. Thanks for the pointers. I use the OCW method and it works very well.

    Offline Erik Cortina

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    Long range load development at 100 yards.
    « Reply #5 on: 10:07 PM, 05/05/13 »
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  • Monte, I have never done an OCW test and only vaguely know how it works from things people have told me.  But the end result is the same it seems. 
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    Online 6BRinNZ

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    Long range load development at 100 yards.
    « Reply #6 on: 12:25 AM, 05/06/13 »
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  • Thanks Eric - info greatly appreciated.

    Couple of questions - have you seen cases where the fps doesn't flatten despite the vertical aligning on the target? If so, do you simply rinse and repeat to validate?
    Could you post this pictures example of the fps? (Maybe the numbers aren't appropriate to post?)

    Offline Erik Cortina

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    Long range load development at 100 yards.
    « Reply #7 on: 05:36 AM, 05/06/13 »
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  • So far, the speed has always flattened out when the groups align.

    I no longer print the chronograph readings, I just make notes on the target now.
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    Offline Toolbreaker

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    Long range load development at 100 yards.
    « Reply #8 on: 08:28 AM, 05/06/13 »
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  • Thanks for posting this, Erik. I've recently been developing loads at 100 yds for shooting at ~700 and have been culling charge weights & confirming the smallest groups for the longer ranges, just as you wrote. I think I need to go back & look at my previous targets & data a little closer now.

    As a side note, I had read online that VLDs won't group well at shorter ranges, but I have been seeing just the opposite with some loads in my testing. I'm thinking that the instability you're describing and my personal grouping of VLDs may be related? Or am I way off here?

    Offline tenring

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    Offline Erik Cortina

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    Long range load development at 100 yards.
    « Reply #10 on: 09:04 AM, 05/06/13 »
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  • Thanks for posting this, Erik. I've recently been developing loads at 100 yds for shooting at ~700 and have been culling charge weights & confirming the smallest groups for the longer ranges, just as you wrote. I think I need to go back & look at my previous targets & data a little closer now.

    As a side note, I had read online that VLDs won't group well at shorter ranges, but I have been seeing just the opposite with some loads in my testing. I'm thinking that the instability you're describing and my personal grouping of VLDs may be related? Or am I way off here?

    VLD's shoot well at 100 yards, I have done it many times.  Go back and examine your targets and you will find a good load.
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    Online zfastmalibu

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    Long range load development at 100 yards.
    « Reply #11 on: 09:07 AM, 05/06/13 »
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  • Eric, after you tune the load in with seating depth do thy still all print the same on target?  Also how do you settle on powder charge, as you have a 1 gr window there?
    Alex

    Offline Erik Cortina

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    Long range load development at 100 yards.
    « Reply #12 on: 09:15 AM, 05/06/13 »
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  • Eric, after you tune the load in with seating depth do thy still all print the same on target?  Also how do you settle on powder charge, as you have a 1 gr window there?
    Alex

    Yes, after adjusting seating depth they still print the same vertically.

    I always load to the center of the window.  For this gun, my load is 40.0 grains.
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    At some point, the shooter becomes the limiting factor in accuracy!

    Offline sailhertoo

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    Long range load development at 100 yards.
    « Reply #13 on: 11:32 AM, 05/06/13 »
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  • I found this target, and I think it's a perfect example of how some people might choose the wrong load because they fell in love with a group without reading the groups properly.  This target was shot with my 6.5x47 Lapua and 139 gr. Lapua Scenars with VV N550 powder.

    At plain sight, 38.5 gr. appears to be the best group, but if you look at the groups next to it they don't hit the target on the same place vertically in relation to the bull's eye.   The load is not stable and this load would cause problems when moving further out because it is not inside the accuracy node.

    However, loads 39.5, 40.0, and 40.5 are vertically in the same place in relation to the bull's eye.  This is the accuracy node for powder charge, my next step would be to load 40.0 gr. and adjust seating depth and bring the group in and done, I now have a load that would shoot out to 1,000 yards.  Also, when the groups line up vertically, the speed also varies very little over the chronograph for the loads that line up on target, it appears that the speed flat lines for a while before it starts to jump up again, this is where you want to be.



    I must be reading this wrong.

    38.5 looks like one hole. how can 39.5, 40, 40.5 align vertically any better than that? They have some vertical to them and 38.5 don't.

    Offline Erik Cortina

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    Long range load development at 100 yards.
    « Reply #14 on: 11:39 AM, 05/06/13 »
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  • You need to read the groups, not shots on the group.

    Like I said, most people will go with 38.5 and they will be wrong. 
    Look at 38.0 and 39.0, the groups don't line up with 38.5 vertically.

    Now, look at 39.5 - 40.5, the groups line up vertically on the target. 
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