LADDER LOADS

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  • Last Post 26 November 2007
CB posted this 15 November 2007

After hearing about Audette's ladder load development and seeing Joe B's attempt at shooting it at 100yds instead of Audette's 300yd test, I decided to give it a try for myself at 100yds. Anyone wanting to know how it works can go to this address on the web to read an excellent article by Randolph Constantine:  http://www.washtenawsportsmansclub.org/groups/cba/downloads/incredload.pdf>http://www.washtenawsportsmansclub.org/groups/cba/downloads/incredload.pdf

Having shot 3 different powders in championship loads in NT2004, NT2005 and NT2006, I knew what load worked with the 3 powders, so now it'll be easier to look into the ladder load results.  The rifle is my Savage M12VBSS in 308Win. and the CB is a Egan MX4-30ARD, 214gr., 1.296” long.  In the attachment below, the bull target on the left is the load I used in NT06 with Vihtavouri N135 powder at 30.5gr behind the MX4-30ard, shot this day. The wind was gusty the day I shot, so I held conditions for the 4 shots in the cluster and 1 shot out to see just how far the wind gust would take it right. Aim point was the dot.

The middle grid target was the actual 14-shot group with 1ea. loads in .25gr increments from 28gr to 31.25gr. The grid target on the right shows the impacts in sequence.

The Bar-line graph below lists the sequence number, vertical impact position from the lowest shot to the highest shot in the range, the powder charge and the velocity. Looking directly at shot #11,12,& 13, they are the tightest clump in the graph, right where my best load is that I call the 'primary load'. There is also another larger group together at shots #1,2, & 3 which is probably a 'secondary load' which probably isn't as efficient as the higher pressure load at #11,12,& 13. Even though the group looks fair in size, it doesn't show just how dispersed the shots are from #3 - 10. In this instance, the shots went higher in elevation with the powder charge increase................Dan

 

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CB posted this 15 November 2007

This ladder load result was shot with my NT05 load of Vihtavouri N130 powder. The target on the left was shot at .2gr less than the NT06 load of 26.8gr, on the day of the ladder shots to get an idea of the conditions. Wind was slight and in&out.

This time I aimed along the horizontal line as the shots began to cluster on the grid target, so horizontal dispersion is of no relevance here, just vertical impacts. The sequence of shots is circled next to each hole. This time I shot 17 loads again of 1ea. in .25gr increments from 23gr to 27gr. I watched for high pressure signs as I went over what I'd shot before at 26.8gr.

Again the bar-line graph lists the sequence number, vertical impact position in the range, powder charge and velocity. Looking at the grid target it is apparent that the load never settled down from #1-7 or 8.  The last shots #10-17 would be in a 1” vertical group. I'd say another ladder load could be shot with charges from #10 in .25gr increments up to 28gr since I never got any high pressure signs. Notice this time that the shots impacted lower as the powder charge incresed..............Dan

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linoww posted this 15 November 2007

Do you think it is a viable alterative to working up a load the “standard” way? Your collected data format was pretty clear compared to the first post on the subject. It was also interesting to see that is backed up you sweet spot match load. I have worked loads up with “new to me powder" up from starting until my chronograph SD's were consistent and the elevation leveled out. Sort of the same thing? Generally from experience I may know a velocity level that works with a certain cartridge/bullet combination and work towards that.I usually can get there pretty fast by fine tuning up or down. I do most of my load testing at 200 yds. In good conditions it seems to show group “shapeâ€? and tendencies very well compared to 100 yds. I think Audette's 300 yd testing allowed these things to show up clearly with jacketed loads. The problem is we have so much “going on” with conditions with our cast bullets at 300 that it may be hard to evaluate it properly at that distance.

 

Geo.

 

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CB posted this 15 November 2007

Yah Geo., I consider that ladder load development is for the 'new to me” powder and the 'new to me' rifle, not an alternative way to develop 'the' load. With CB loads, the ambient influences at 200yds is a greater variable than the influences in the variable load. You always need to consider all the forces in CB shooting, which is greater and which is more important. Ladder load development ought to always be shot under good conditions to let the loads show us their variations.

 I think ladder load development is also a good comparison between powder selection with all other components left the same. It seems most accurate loads are not necessarily the best ES and SD, but a bar-line graph comparison could show what powder has a milder accuracy width over an erratic accuracy width.

I deal with horizontal dispersion when fine tuning with 5-shot groups, where often times a diagonal group will come in with another .1 or .2gr increase in powder charge.....................Dan

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linoww posted this 15 November 2007

"It seems most accurate loads are not necessarily the best ES and SD"

 

I had a great load (this was .222 with jacketed loads) I decided to chronograph. When I got the data I was  surprised by the horrible variation! I tried to fine tune up and down and the accuracy got worse in both cases. I now base my cast bullet load data on a large number of groups fired with a point of impact overlay of a large number of groups from the same session. If I get a “wandering zeroâ€? with good individual groups I look at cleaning techniques or lube. This is assuming good conditions.What do you go with, a bit larger group or one that puts a larger percentage at the aiming point??

 

George.

 

 

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billwnr posted this 15 November 2007

Dan, the short response is, “I am impressed.” Dang, this is easy to figure out and understand. Thanks.

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CB posted this 15 November 2007

Joe, here is another ladder load result for ya. This ladder load result was shot with my NT04 load of 28.75gr of H4895 powder. The bull target on the left is a 5-shot group shot just before the ladder shots to get an idea of the conditions. Wind was slight.

The grid target in the center is the actual shot target and the grid target on the right shows the impacts in sequence.  This time I shot another 17 loads again of 1ea. in .25gr increments but now from 27gr to 31gr.

The bar-line graph lists the sequence number, vertical impact position in the range, powder charge and velocity. The plotted dots of shots number 8, 9, 14, 15, and 16 are shaded in gray because I could not see the impacts, as they were somewhere inside the cluster. The primary load looks like it shows up in shots 7, 8, & 9. Looks like secondary load at shots 2, 3, & 4 and also another accurate spot up at shots 14, 15, & 16 though they are guessed at their impact in the cluster. Since I could not plot 5 of the impacts, I shot another ladder load using H4895................Dan

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CB posted this 15 November 2007

I do pretty much the same as Dan.. The only difference is I load up at the range so I can repeat if necessary a group. I always shoot a min of 6 or 7 shot groups of the same charge with a clean barrel then a couple of foulers. Don't pay much attention to horizontal, only the vertical.

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CB posted this 15 November 2007

This is the second ladder load result shot with 28.75gr of H4895 powder. The bull target on the left is a 5-shot group the day of the ladder shots to get an idea of the conditions. Wind was slight and in&out.

The grid target is the actual shot target and this time I aimed along the horizontal line as the shots began to cluster on the grid target, so horizontal dispersion is of no relevance here, just vertical impacts. The sequence of shots is circled next to each hole. This time I shot another 17 loads again of 1ea. in .25gr increments from 27gr to 31gr.

The bar-line graph lists the sequence number, vertical impact position in the range, powder charge and velocity. The primary load this time looks like it shows up in shots 6, 7, & 8 and another at shots 9, 10, & 11. The high group at shots 14, 15, & 16 look like a weak accurate load, but I think deserves further 5-shot group development.  I think it's interesting again to see both of the H4895 impacts go lower as velocity increases at 100yds.................Dan

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CB posted this 16 November 2007

Dan;

What measure/scale/? do you use to get powder in .25 grain increments?

Thanks;

joe b.

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CB posted this 16 November 2007

joe b.,

I use my old Redding / oil reservoir scale. It has a grad scale out at the pointer. I set the scale on .2 & .7 of the whole grain and trickle just high (heavy) above the center mark. Ideally the pointer would rest between the two marks, center mark and +.1 mark. It isn't much, just a few kernels of powder so I get real particular and just just call it a, “heavy center” rather than light, under the center mark............Dan

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Idaho Sharpshooter posted this 25 November 2007

Very interesting data accumulation. What cartridge and bullet length is shown here? What were the velocity increases from start to finish? Were they linear, or did you see an uneven increase? Utilizing the scale that way was very creative thinking. I am always curious as to what going up in .25gr increments might show as opposed to the usual .2 for small cases and .5gr for bigger ones. I think I have about two months worth of work ahead of me, and lots of bullets to cast.

Rich

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CB posted this 26 November 2007

Idaho Sharpshooter wrote: Very interesting data accumulation. What cartridge and bullet length is shown here? What were the velocity increases from start to finish? Were they linear, or did you see an uneven increase?

Rich,

This is my Savage 308Win. The CB is an Egan MX4-30ARD at 214gr with Lino, 1.296” long. The velocity range is in a colum on the right side of the graph................Dan

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Idaho Sharpshooter posted this 26 November 2007

Thank you Dan! I thought so, but am not willing to “assume” anything at this point.

Thanks to all of you for sharing...

Rich

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Ken Campbell Iowa posted this 26 November 2007

great Stuff, Dan ....   thanks ... sure does a guy wonders on a cold winter day to see groups of bullets trying to make one big hole ... heh heh, hope nobody analyizes that thought and makes a statistical probability / data report on it (g).

Think I'll take the rest of the day off and go play with my gun stuff ... I don''t think I have a rig in the place that shoots cast bullets under 2 moa !!  ( just by co-incidence the width of a bean can at 100 yards ....    )

thanks again, ken at deltawerkes

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